Sayyidah Busrah bint Safwan (may Allah be pleased with her) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever touches his private part, or his testicles, or his groin, let him perform ablution."
(b) In the narration of al-Tusi the words are: "or touches his groins, let him perform ablution like the ablution for prayer."
Ali bin Umar al-Hafiz (may Allah have mercy on him) said: Abd al-Hamid bin Ja'far erred in mentioning the testicles and the groin and in inserting that into the hadith of Sayyidah Busrah (may Allah be pleased with her) from the Prophet (peace and blessings be upon him); what is preserved is that this is the saying of Urwah, not attributed to the Prophet, and that is how the trustworthy narrators reported it from Hisham, among them Ayyub al-Sakhtiyani and Hammad bin Zayd.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 652