Sayyidah Busrah bint Safwan (may Allah be pleased with her) said: the Messenger of Allah (peace and blessings be upon him) said: "When one of you touches his private organ, or his testicles, or his groin, let him perform ablution."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20880