hadith

 Sahih Bukhari  صحیح بخاری

Hadith # 2721

Translation:

Narrated Uqba bin Amir (RA): 

Allahs Apostle ﷺ 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."