Sahih al-Bukhari, Hadith 2721 ⓘ
Narrated `Uqba bin Amir: Allah's Messenger 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."
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، حَدَّثَنَا اللَّيْثُ، قَالَ حَدَّثَنِي يَزِيدُ بْنُ أَبِي حَبِيبٍ، عَنْ أَبِي الْخَيْرِ، عَنْ عُقْبَةَ بْنِ عَامِرٍ ـ رضى الله عنه ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَحَقُّ الشُّرُوطِ أَنْ تُوفُوا بِهِ مَا اسْتَحْلَلْتُمْ بِهِ الْفُرُوجَ " .
also referenced under: Book 54, Hadith 10 (In-Book) & Volume 3, Book 50, Hadith 882 (USC-MSA)