Sayyiduna Qatadah Abu Hashim al-Rahawi (may Allah be pleased with him) said: I came to the Messenger of Allah (peace and blessings be upon him) and accepted Islam, and he (peace and blessings be upon him) said to me: "O Qatadah! Take a ritual bath (ghusl) with water and lote-tree leaves, and shave off the hair of disbelief." The Messenger of Allah (peace and blessings be upon him) used to order whoever accepted Islam to be circumcised. He was eighty years old at that time.
Hadith Referenceالمعجم الكبير للطبراني / باب القاف / 16070