Sahih Bukhari
Sahih Bukhari Voluume 003, Book 050, Hadith Number 882.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 50. Conditions
Narated By Uqba bin Amir : Allah's Apostle said, "From among all the conditions which you have to fulfill, the conditions which make it legal for you to have sexual relations (i.e. the marriage contract) have the greatest right to be fulfilled."