Mukhtasar Bukhari

Narrated from Sayyiduna Anas (may Allah be pleased with him), he said: If I wished, I could say that the Prophet (peace and blessings of Allah be upon him) said, but Anas (may Allah be pleased with him) said that it is the Sunnah of the Prophet (peace and blessings of Allah be upon him) that when a man marries a virgin after a widow, he should stay with her for seven days (then alternate between them), and when he marries a widow in the presence of a virgin, he should stay with her for three days (then alternate between them).