It is narrated from Sayyiduna Talq bin Ali (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Whoever touches his private part should perform ablution."
Imam al-Tabarani (may Allah have mercy on him) said: No one narrated this hadith from Ayyub bin Utbah except Hammad bin Muhammad, and Hammad bin Muhammad also narrated the other hadith (with the opposite content), and in my view both are sahih (authentic). It appears that he (Sayyiduna Talq, may Allah be pleased with him) heard the first hadith from the Prophet (peace and blessings be upon him) before this, then heard this hadith later, so his narration came to agree with that of Sayyidah Busrah, Sayyidah Umm Habibah, Sayyiduna Abu Hurayrah, Sayyiduna Zayd bin Khalid al-Juhani (may Allah be pleased with them) and the other Companions who narrated from the Prophet (peace and blessings be upon him) the command to perform ablution after touching the private part. Thus he heard both the abrogated and the abrogating (hadiths).
Hadith Referenceالمعجم الكبير للطبراني / باب الطاء / 8221