“O you who believe! Let not (one) people laugh at (another) people perchance they may be better than they, nor let women (laugh) at (other) women, perchance they may be better than they; and do not find fault with your own people nor call one another by nick names.” (Surah al-Hujurāt 49: 11)
It is quoted in Tafsīr Majmaul Bayan that whenever Thabit bin Qays came to the Holy Prophet’s assembly people used to make way for him and allow him to sit nearest to the Prophet (a.s.) because he was hard of hearing. One day in morning payers he managed to get a place only in the last row. After the prayers he got up and stepping over other people went towards the Messenger of Allah (S) when there remained only one person between him and the Prophet, he said, “Let me go, so that I can sit near the Messenger (S).” The man in between told him to sit where he was. Thabit was angry but he sat down and when it was light he saw the man’s face he asked him who he was. When the man told him his name Thabit said, “So and so, son of so and so’ and mentioned the name of his mother who was notorious for her loose morals before the advent of Islam.
The person was very much ashamed at this and he lowered his head in disgrace. It was then that the above verse was revealed.