One day Imam Musa Kazim (as) was passing by the tent of a Nomad who was a black man. He went up to him and said "Salam-Alaikum", in a warm and friendly manner.
Upon leaving he said good-bye to him in a very kind manner with these words: "If there is anything I can do for you, I'm more than willing to do it".
One of the followers of the Imam who saw this attitude said "Is it suitable for you, the son of the messenger of Allah, to sit and talk with a man of no reputation and make such an offer as: If you need me in any work, I'm more than willing to do it? Is it right for a man of great dignity to talk to a man like that?".
The Imam replied, "This is one of Allah's creatures. Allah has created all men equal. Besides, as a Muslim, he is our brother in faith. After all, life does not remain the same forever. One who needs help today may be the one who will be able to help us tomorrow when we'll need help! If we don't pay any attention to him today, one day when we may need him we will be embarrassed to ask him for help".