Qatadah Abu Hisham narrates: I came to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said to me: O Qatadah! Take a ritual bath with water and lote-tree leaves, and shave off from yourself the hair of the time of disbelief! The narrator says: The Prophet (peace and blessings be upon him) used to order anyone who accepted Islam to be circumcised, even if he was eighty years old.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1563