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
Sayyidah Busrah bint Safwan (may Allah be pleased with her) narrated that she heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever touches his private part, let him perform ablution."
Urwah used to say: "Whoever touches the groin, or the testicles, or the private part, let him perform ablution."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 653
The father of Hisham bin Urwah (may Allah have mercy on him) used to say: When a person touches his groin, or his testicles, or his private part, he should not pray until he performs ablution.
(b) Through another chain, a version with this inserted into the hadith (mudraj) is reported from Hisham bin Urwah (may Allah have mercy on him); this is an error by some narrator, and the correct position is that it is the saying of Urwah (may Allah have mercy on him).
(c) Analogy requires that there be no ablution because of touching; we have only followed the Sunnah in making ablution obligatory for touching the private part, so it is not obligatory for anything else.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 654