Sahih Bukhari | Volume 7 | Hadith Number 238
Narrated by 'Aisha
Rifa'a Al-Qurazi married a lady and then divorced her whereupon she married another man. She came to the Prophet and said that her new husband did not approach her, and that he was completely impotent. The Prophet said (to her), "No (you cannot remarry your first husband) till you taste the second husband and he tastes you (i.e. till he consummates his marriage with you)."