In the Prophet (salAllahu alayhi wasalam)'s time; where men were often cruel to each other, let alone animals, Muhammad (salAllahu alayhi wasalam) taught his Companions that one should be kind to all living things, animal or plant, since they are all part of Allah's creation. He taught that a woman would enter Jahannam (Hell) because she had locked up a cat without giving it anything to eat.
He nursed a sick rooster back to health. He was kind to a cat who liked to sleep in his house every night and used to rise and open the door for it himself. Once when A'isha (radiAllahu anha) was riding a camel who would not obey, she best it, so he said to her, admonishing, 'Gently, A'isha, gently.'
Once a rough and uncouth Arab came to the Messenger and said, 'Muhammad, give me of what Allah has given you.' So the Messenger (salAllahu alayhi wasalam) gave him the money that was on him, then asked if he had enough.
The man answered in a rude manner that it was not enough, nor was it adequete. The Companions wanted to shove the man away or beat him, but the Messenger said, 'No, no, leave him to me.' He took him to his house and gave him more, then asked if this was enough.
The man, well pleased, answered that it was enough and began to thank Allah and His Messenger. The Messenger asked him to go out to the Companions and to tell them that he was satisfied, for they many have resented his former behaviour. the man did so.
When the Messenger (salAllahu alayhi wasalam) met his Companions later he explained to that to them by means of an allegory. He said that there was once a man who had a recalcitrant camel that had run away from him. People kept trying to bring it back to him by pulling or beating it, but he asked them not to interfere between him and his camel.
He then took some bush and kept gicing it to the camel little by little until the camel came back to him again. he concluded the story by saying that had they beat or rough-handled the man, it would not have helped him towards faith, but if he left content he had a better chance of coming closer to faith.
One day while he was teaching a group of people a little bird kept hovering over his head. He stopped and asked, 'Who has deprived this poor bird of its chick?' A little boy in the group said, 'It was I, Messenger of Allah.' Whereupon the Messenger (salAllahu alayhi wasalam) instructed him to return the chick immediately.