Sunan At-Tirmidhi

Abu Qilabah narrated from Anas bin Malik, :He (Abu Qilabah) said: ""If I wish, I could say: 'The Messenger of Allah said'"" but he said: ""The Sunnah when a man married a virgin after he already has a wife, is that he stays with her seven (nights). And when he married a matron when he already has a wife, he stays with her three (nights)