It is narrated from Sayyida Aisha (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) came to her, and at that time a man was sitting with her. The blessed face of the Prophet changed, and signs of displeasure appeared on his blessed countenance. She said: "This is my milk-brother." The Messenger of Allah (peace and blessings be upon him) said: "Investigate carefully who your (foster) brothers are. Suckling is only considered valid when the milk is drunk at the time of hunger."