Urwah bin al-Zubayr said: I went to Marwan bin al-Hakam, and he mentioned the things that make ablution necessary. Marwan said: Busrah bint Safwan (may Allah be pleased with her) told me that the Messenger of Allah (peace and blessings be upon him) said: "Whoever touches his penis, let him perform ablution."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20866