I speak here of people like the prophets, or men of God down through the ages.

Lets look at Abraham.  He knew that he was going to have a child.  God promised him that.  But how long would he have to wait for the fulfilment of the promise.
When Abraham was 75 years old God told him that his descendants would have the land.

Gen 12:4  So Abram departed, as the LORD had spoken unto him; and Lot went with him: and Abram was seventy and five years old when he departed out of Haran. 

Gen 12:7  And the LORD appeared unto Abram, and said, Unto thy seed will I give this land: and there builded he an altar unto the LORD, who appeared unto him. 

When Abraham had no child from Sarah, she said to Abraham to take Hagar and perhaps he would have a child through her.

Gen 16:2  And Sarai said unto Abram, Behold now, the LORD hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai. 

When Abraham was 86 years old Hagar bore Ishmael.

Gen 16:16  And Abram was fourscore and six years old, when Hagar bare Ishmael to Abram. 

Abraham and Sarah had waited 10 years since God had told Abraham his descendants would have the land.  These must have been very long and hard years, as Abraham and Sarah were getting older, and still no sign of Sarah becoming pregnant.
When Abraham was 99 the Lord appeared to him and Sarah and told them they would have a son, this seemed impossible to Abraham and Sarah, and Abraham laughed, and so did Sarah.

Gen 17:17  Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear? 

Gen 18:12  Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also? 

God said is anything too hard for the Lord.

Gen 18:14  Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son. 

Notice in the above scripture, the words at the appointed time, this is very interesting and we need to note, that God has a time appointed when He will do certain things, in this case it was when He decided to act on behalf of Sarah and allow her to become pregnant.
He could have acted 25 years earlier, but He wanted to see how Sarah and Abraham acted and if they would wait patiently on the Lord.

Isaac was born to Abraham and Sarah when Abraham was 100 years old and Sarah was 90 years old.

Gen 21:5  And Abraham was an hundred years old, when his son Isaac was born unto him. 

It had been 25 years since God had first spoken to Abraham, about having a child.
This may seem as nothing to us, but put yourself in their shoes, both were way beyond the years of child bearing, Abraham was 75 years old and Sarah 65 years old, at the time God first spoke to him. If you know anyone of this age, how hopeless it would seem for them to have a child.  This is what both Abraham and Sarah, had to endure, we need to try to put ourselves in their position and see how hard it must have been for them.  God was testing them, He wanted to see if they would wait on God.   Sometimes this is an extremely hard test, in this case it was very very difficult.
God wants us to exercise faith in Him, and not to use our own human reasoning, we must just accept that God will do as He has promised and wait, no matter how long that takes. 

Now lets look at David.

God tells Samuel that one of the sons of Jesse will be king.

1Sa 16:1  And the LORD said unto Samuel, How long wilt thou mourn for Saul, seeing I have rejected him from reigning over Israel? fill thine horn with oil, and go, I will send thee to Jesse the Bethlehemite: for I have provided me a king among his sons. 

Samuel invites Jesse and his sons to the sacrifice

1Sa 16:5  And he said, Peaceably: I am come to sacrifice unto the LORD: sanctify yourselves, and come with me to the sacrifice. And he sanctified Jesse and his sons, and called them to the sacrifice. 

However, Samuel was looking at their outward appearance and not on their heart.

1Sa 16:7  But the LORD said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for the LORD seeth not as man seeth; for man looketh on the outward appearance, but the LORD looketh on the heart. 

David was not even invited to the sacrifice, he had to tend the sheep.

1Sa 16:11  And Samuel said unto Jesse, Are here all thy children? And he said, There remaineth yet the youngest, and, behold, he keepeth the sheep. And Samuel said unto Jesse, Send and fetch him: for we will not sit down till he come hither. 

When David was anointed king he must have been a very young man, possibly about 17 years old.

1Sa 16:12  And he sent, and brought him in. Now he was ruddy, and withal of a beautiful countenance, and goodly to look to. And the LORD said, Arise, anoint him: for this is he. 

This scripture is after David was anointed king, and he was a youth

1Sa 17:33  And Saul said to David, Thou art not able to go against this Philistine to fight with him: for thou art but a youth, and he a man of war from his youth. 

Notice the attitude that David had, he knew he was going to be king one day, and yet he remained humble, even when he was going to marry the kings daughter. 

1Sa 18:18  And David said unto Saul, Who am I? and what is my life, or my father's family in Israel, that I should be son in law to the king? 

Saul had a very bad attitude towards David as the following scripture shows, and it must have been very difficult for David to live with his attitude. 

1Sa 18:29  And Saul was yet the more afraid of David; and Saul became David's enemy continually. 

David spent a great deal of time on the run from Saul

1Sa 21:10  And David arose, and fled that day for fear of Saul, and went to Achish the king of Gath. 

David had no desire to harm Saul, even though Saul wanted to kill David, he respected the office.

1Sa 26:9  And David said to Abishai, Destroy him not: for who can stretch forth his hand against the LORD'S anointed, and be guiltless? 

2Sa 1:14  And David said unto him, How wast thou not afraid to stretch forth thine hand to destroy the LORD'S anointed? 

David patiently waited for his time to come when he would be king, he knew this would happen one day, he had faith, and trusted God to bring it about when God decided it was the appointed time for him to become king. 
David had to wait more than 10 years after he was anointed king before he began to reign.
David did not try to take these things into his own hands and make them happen when he wanted them to.

2Sam 5:4  David was thirty years old when he began to reign, and he reigned forty years.

No wonder God loved David, and said this wonderful legacy about him.

Act 13:22  And when he had removed him, he raised up unto them David to be their king; to whom also he gave testimony, and said, I have found David the son of Jesse, a man after mine own heart, which shall fulfil all my will. 

This next account  about Moses, covers a time which is little known by most, and may be new knowledge to most readers of the bible.

At this time Moses was living in Egypt.

Act 7:23  And when he was full forty years old, it came into his heart to visit his brethren the children of Israel. 

Moses defends the Israelite and kills the Egyptian.

Act 7:24  And seeing one of them suffer wrong, he defended him, and avenged him that was oppressed, and smote the Egyptian: 

Now notice the following verse, this is very interesting, why would Moses have thought that the Israelites knew that God was going to use him, to deliver the Israelites. 
The reason for this is that God had already spoken to Moses about this, and told him, that He was going to bring the Israelites out of captivity through Moses.

Act 7:25  For he supposed his brethren would have understood how that God by his hand would deliver them: but they understood not. 

The next verse shows that God had indeed spoken to Moses beforehand, Moses said that he was not good at speaking, neither now nor since God had first spoken to him. 

Exo 4:10  And Moses said unto the LORD, O my Lord, I am not eloquent, neither heretofore, nor since thou hast spoken unto thy servant: but I am slow of speech, and of a slow tongue. 

So now we come to the question  how long was it from the time God initially spoke to Moses about the deliverance of the  children of Israel and the time that God actually delivered them.  How long was it that Moses had to live humbly with this knowledge that God was going to use him to deliver the nation of Israel.
Moses had to learn patience, remain humble, develop faith that God would keep His word to him regarding the Israelites, he had to make sure he did not use human reasoning and try to make it all happen when he wanted to instead of waiting for God to act, at the appointed time.

The following scripture shows that Moses had to wait 40 years from the time that God first spoke to him about the Israelites.

Act 7:30  And when forty years were expired, there appeared to him in the wilderness of mount Sina an angel of the Lord in a flame of fire in a bush. 

It would appear that Moses did wait patiently on the Lord.

Now lets look at Jesus.  He was very smart and learned in Gods word at the tender age of 12

Luk 2:42  And when he was twelve years old, they went up to Jerusalem after the custom of the feast. 

Luk 2:47  And all that heard him were astonished at his understanding and answers. 

However, we do not read much about the life of Jesus until it was time for Him to start His ministry.
Notice the following scripture which shows that He had an appointed time to start His work.

Joh 2:4  Jesus saith unto her, Woman, what have I to do with thee? mine hour is not yet come. 

So we see that Christ Himself had to wait until the time appointed for His ministry to start.
Another example of Christ waiting for the appointed time.

Joh 7:8  Go ye up unto this feast: I go not up yet unto this feast; for my time is not yet full come. 

We need to be patient and wait for God, He is in charge, He will decide when things will happen…..not us.

What happens if we don’t wait on the Lord

Some people have chosen not to wait on God, and to take matters into their own hands, for example we see in the following verses what happened regarding Saul when he decided he knew best.

Lets look at the example of Saul.

Saul had been told to kill everything and he said that he had done this.

1Sa 15:13  And Samuel came to Saul: and Saul said unto him, Blessed be thou of the LORD: I have performed the commandment of the LORD. 

Samuel heard the animals and asked what about these

1Sa 15:14  And Samuel said, What meaneth then this bleating of the sheep in mine ears, and the lowing of the oxen which I hear? 

Saul said that the animals were for an offering

1Sa 15:15  And Saul said, They have brought them from the Amalekites: for the people spared the best of the sheep and of the oxen, to sacrifice unto the LORD thy God; and the rest we have utterly destroyed. 

When Saul was humble he was anointed King, then that attitude changed.

1Sa 15:16  Then Samuel said unto Saul, Stay, and I will tell thee what the LORD hath said to me this night. And he said unto him, Say on. 
1Sa 15:17  And Samuel said, When thou wast little in thine own sight, wast thou not made the head of the tribes of Israel, and the LORD anointed thee king over Israel? 

Sauls instructions were clear, why did he disobey and seize the spoil?

1Sa 15:18  And the LORD sent thee on a journey, and said, Go and utterly destroy the sinners the Amalekites, and fight against them until they be consumed. 
1Sa 15:19  Wherefore then didst thou not obey the voice of the LORD, but didst fly upon the spoil, and didst evil in the sight of the LORD? 

Saul replied that he brought back Agag and blamed the people for bringing back the spoil.

1Sa 15:20  And Saul said unto Samuel, Yea, I have obeyed the voice of the LORD, and have gone the way which the LORD sent me, and have brought Agag the king of Amalek, and have utterly destroyed the Amalekites. 
1Sa 15:21  But the people took of the spoil, sheep and oxen, the chief of the things which should have been utterly destroyed, to sacrifice unto the LORD thy God in Gilgal. 

Samuel showed Saul that to obey and listen, were to be desired over sacrifice.

1Sa 15:22  And Samuel said, Hath the LORD as great delight in burnt offerings and sacrifices, as in obeying the voice of the LORD? Behold, to obey is better than sacrifice, and to hearken than the fat of rams. 

Saul paid a huge penalty, he was rejected as being king, look what God said about his rebellion.

1Sa 15:23  For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from being king. 

To wait on the Lord is very important, we must not take matters into our own hands, we must be patient and obey and listen to all the instructions of the Lord, our hearts and motives must be pure in this regard.  The penalties are severe as shown above.

We see that all of Gods chosen servants have had to wait and be patient, they have been tested to see if they will wait for God to act, or just take things into their own hand.  We must wait on God, He knows best.

It is a good test for us to wait, to develop faith and patience and to trust in God, He will act at the appointed time.