Sahih Bukhari Volume 003, Book 034, Hadith Number 265.
Narated By Anas : When Abdur-Rahman bin Auf came to Medina, the Prophet established a bond of brotherhood between him and Sad bin Ar-Rabi al-Ansari. Sad was a rich man, so he said to 'Abdur-Rahman, "I will give you half of my property and will help you marry." 'Abdur-Rahman said (to him), "May Allah bless you in your family and property. Show me the market." So 'Abdur-Rahman did not return from the market) till he gained some dried buttermilk (yoghurt) and butter (through trading). He brought that to his house-hold. We stayed for some-time (or as long as Allah wished), and then Abdur-Rahman came, scented with yellowish perfume. The Prophet said (to him) "What is this?" He replied, "I got married to an Ansari woman." The Prophet asked, "What did you pay her?" He replied, "A gold stone or gold equal to the weight of a date stone." The Prophet said (to him), "Give a wedding banquet even if with one sheep."