Sahih Muslim Book 8, Hadith Number 3319.

Anas b. Malik reported that Allah’s Apostle (May peace be upon him) saw the trace of yellowness on ‘Abd al-Rahman b. ‘Auf and said: What is this? Thereupon he said: Allah’s Messenger, I have married a woman for a date-stone’s weight of gold. He said: God bless you! Hold a wedding feast, even if only with a sheep.