Musannaf Ibn Abi Shayba 9:1256

Abu Bakr narrated to us, he said: Mu'adh ibn Mu'adh narrated to us, from Humayd, from Anas, that the Prophet (peace and blessings of Allah be upon him) said to Abd al-Rahman: "Give a wedding feast, even if it is with a sheep," meaning when he got married.