Sahih Muslim Book 4, Hadith Number 2131.

Chapter : The Apostle of Allah (way peace be upon him) seeking permission from the Lord. the Exalted and High, for visiting the grave of his mother.

Ibn Buraida reported on the authority of his father that the Messenger of Allah (may peace be upon him) said: I forbade you to visit graves, but you may now visit them; I forbade you to eat the flesh of sacrificial animals after three days, but you way now keep it as long as you feel inclined; and I forbade you nabidh except in a water-skin, you may drink it from all kinds of water-skins, but you must not drink anything intoxicating.