His Parents & Birth:
Mother:

Umme Hamida was a slave girl who was brought to Madina and bought by the 5th Imam for his son for 17 dirhams. The first thing that he told her was : "You are Hamida (the praised one) in this world and Mahmuda (praiseworthy) in the hereafter".
When the women of Madina used to come to the 6th Imam to ask masails he used to send them to Umme Hamida saying: "Her answers will be those given by me".

Imam Musa Al-Kadhim (a.s.) was born in Abwa (a place between Mecca and Madina). It is here that Bibi Amina (Prophet Muhammad's (S.A.W.) mother) is buried. Imam was born when his parents were returning from Mecca. As soon as he was born he did Sajda reciting Kalima and bearing witness to the Imaamate of all the other Imams including his own.

Childhood

He is one of the Imams whose miracles in childhood are reported extensively. Imam Ja'fer As-Sadiq (A.S.) repeatedly pointed out Imam Musa Al-Kadhim (a.s.) as his successor because he knew of the people who after his death would differ.
(N.B. The Ismailis say Ismail (Imams eldest son who died whilst Imam Ja'fer Sadiq (a.s.) was still alive) was the 7th Imam. One of the 6th Imam's other sons - Abdullah also claimed Imaamate.)

Yaqub Al-Saraaj visited the 6th Imam once who told him to greet his son Musa who was a week old in his cradle. Imam Musa replied to the salaam and told Yaqub to change his daughters name (Humayra) as it was a name not liked by Allah.

Safwan (a companion of the 6th Imam) once saw the young Imam Musa teaching the lamb he was playing with to prostrate to Allah.

Once when Imam was 5 years old, Abu Hanifa came to visit the 6th Imam. He asked Imam Musa (a.s.): "O son of the Prophet! What is your opinion about the deeds of man? Does he do them on his own free will or does God make him do them?".
The 7th Imam replied : "The doings of man can have three possibilities:

1.      God compels a man to do them whilst he is helpless.

2.      Both God and man share the commitment.

3.      Man does them alone.

If the first is true than God cannot punish man for sins he did not commit.
If the second is true than too God cannot punish man for he is an equal partner.
Then, we are naturally left with the third, that man is absolutely responsible for his own doings".

His Titles

(These were used to avoid using Imams name as the very mention of it would lead to arrest, torture, harassment and/or death.)
Babul Hawaaij (Door of fulfilment of needs). Even after his death people have their needs fulfilled and do not return empty handed from his shrine (Ask especially for cure of physical illnesses, especially eyes).
Kadhim (One who swallows his anger). Imam Musa (a.s.) lived in an era when the rulers were the cruellest ever. Their hatred for the Ahlul Bayt and their followers was intense. Imam's followers were constantly harassed and tortured. The last 19 years of his life was spent in prison. Despite all these hardships, he was always patient spending entire nights in the worship of Allah. His character even converted the prison wardens towards him.

His Life & Works (Imamate)

When his father was martyred (poisoned by the ruler Mansur Dawanaqi), Mansur asked the governor of Madina to behead all the trustees Imam had left. The governor (called Sulayman) wrote back to say that the 6th Imam had left 5 trustees of whom he (Mansur) was the first and Sulayman the second followed by Abdullah, Umme Hamida and Imam Musa (a.s.). Mansur kept quiet.
After the 6th Imam's death Mansur encouraged the Ismaili sect to develop although he knew that Ismail had died 20 years before. At the same time the 6th Imam's other son Abdullah claimed Imamate (however he only lived 17 days after that).
Mansur was busy building Baghdad after that (although the torture and killing of the followers of Ahlul Bayt continued) and left Imam Musa (a.s.) for a while in which Imam had a little time to teach true Islam.
When Mansur died his son Mahdi came to power in 158 a.h. He increased the atrocities on the family and followers of Ahlul Bayt. Imam Musa (a.s.) advised his followers to practise Taqiyya (meaning not to show ones faith outwardly). Mahdi called Imam to Baghdad and imprisoned him releasing him after a while.

After Mahdi came his son Musa who assumed the title Haadi. He only ruled for 15 months but the atrocities continued.

After the death of Haadi came his brother Harun Rashid. It was he who introduced Backgammon, Chess and Music as Islamic culture (they are Haraam). Harun was told of the popularity of Imam Musa (a.s.) by Muhammad bin Ismail (Imam's nephew) and about the collection of khums.

Harun was furious and wanting to prove his relationship to the Prophet went to the Prophets grave and greeted the Prophet addressing him as his uncle. Imam Musa (a.s.) was there and he addressed the Prophet as his grandfather. Imam then asked Harun that if the Prophet were to come and ask Harun for his daughters hand in marriage would he agree?
Harun said "Yes". Imam said "That is the difference between you and me - my daughter would be haraam for the Prophet (mahram)".
Harun had Imam arrested in the Prophet's mosque whilst Imam was praying. He was handcuffed and shackled and sent to Basra. A similar caravan was sent to Baghdad to fool Imam's followers. Imam was put into prison under the custody of Isa bin Ja'fer. After a year Isa wrote to Harun saying he could no longer imprison Imam as he could find only piety and righteousness in him.
Harun had Imam moved to Baghdad under the custody of Fadhl bin Rabi who too became a follower of Imam. The prisons were so small that there was no room to stand and the food was a cup of water and two pieces of dry bread a day. Imam remained patient.
Harun also hired people to kill Imam (It is reported that they were from England). They too on seeing Imam cried and refused to murder him even though they were paid to do so.
Harun finally moved Imam in the care of Sindi bin Shahak (a very cruel man). Imam remained in prison for the last 19 years of his life.

The 19 years of imprisonment gave the Shia population a little relief as the rulers concentrated on Imam. It enabled the Shias to disperse from Arabia to Iran, India etc. thus spreading Islam and it was one of the factors towards the popularity of the 8th Imam.

Summary of his Life Works

In a situation in which the family and followers of the Ahlul Bayt were being murdered and tortured Imam taught the true word of Allah. Through his character and piety he showed the meaning of tabligh living up to the hadith of the 6th Imam:
"Acquire a true Muslim character and that shall spread Islam".

In 183 a.h. Sindi had Imam killed with poisoned dates. Another narration says Imam was wrapped in a carpet and he was suffocated and stamped on. His body was left on the bridge of Baghdad and an announcement was made for all to come and see him.

N.B. It was a ploy to encourage Shias to come out in anger so they could be identified.

When Harun Rashid's brother Sulayman heard of this he was furious and arranged for his burial in a Quraysh cemetery outside Baghdad (the 8th Imam gave ghusl and kafan). A town grew around the tomb of Imam called Kadhmain (meaning the two Kadhims) since the 9th Imam is also buried there.

His Children

He had 19 sons & 18 daughters. The most famous of his sons is his successor, Imam Ali Ar-Ridha (a.s.) and the most famous of his daughters is Fatima Kubra known as Masuma Qum who is buried in Qum.