Sahih Bukhari Volume 005, Book 058, Hadith Number 125.

Narated By Anas : When 'Abdur-Rahman bin 'Auf came to us, Allah's Apostle made a bond of fraternity between him and Sad bin Ar-Rabi' who was a rich man, Sad said, "The Ansar know that I am the richest of all of them, so I will divide my property into two parts between me and you, and I have two wives; see which of the two you like so that I may divorce her and you can marry her after she becomes lawful to you by her passing the prescribed period (i.e. 'Idda) of divorce. 'Abdur Rahman said, "May Allah bless you your family (i.e. wives) for you." (But 'Abdur-Rahman went to the market) and did not return on that day except with some gain of dried yogurt and butter. He went on trading just a few days till he came to Allah's Apostle bearing the traces of yellow scent over his clothes. Allah's Apostle asked him, "What is this scent?" He replied, "I have married a woman from the Ansar." Allah's Apostle asked, "How much Mahr have you given?" He said, "A date-stone weight of gold or a golden date-stone." The Prophet said, "Arrange a marriage banquet even with a sheep."