Sayyiduna Ali (may Allah be pleased with him) narrates that when Hasan was born, he was named Hamza, and when Husayn was born, he was named Ja'far after his uncle. Later, the Prophet (peace and blessings be upon him) called me and said: "I have been commanded to change their names." I submitted, "Allah and His Messenger know best." Thus, the Prophet (peace and blessings be upon him) named them, respectively, Hasan and Husayn.