Abd al-Rahman bin Abi Layla (may Allah have mercy on him) said: We were with the Prophet (peace and blessings be upon him) when Sayyiduna al-Hasan (may Allah be pleased with him) came and began rolling about on him. He (peace and blessings be upon him) lifted up his shirt and kissed his little private part.
The chain of this report is not strong, and it does not state that he (peace and blessings be upon him) touched it with his hand and then prayed without performing ablution.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 651