Hadith 5311
Lady Aisha Siddiqa (may Allah be pleased with her) narrates: On the seventh day after the birth of Sayyiduna Hasan (may Allah be pleased with him) and Sayyiduna Husayn (may Allah be pleased with him), the Prophet Muhammad (peace and blessings be upon him) performed their 'aqiqah and named them. He ordered that the harmful thing (i.e., the hair) be removed from their heads.