Source:
https://sunnah.com/adab:1183"It is related that Abu Hurayra said, "I never sae al-Hasan without my eyes overflowing with tears. That is because the Prophet, may Allah bless him and grant him peace, went out one day and he found me in the mosque. He took my hand and I went along with him. He did not speak to me until we reached the market of Banu Qaynuqa'. He walked around it and looked. Then he left and I left with him until we reached the mosque. He sat down and wrapped himself in his garment. Then he said, 'Where is the little one? Call the little one to me.' Hasan came running and jumped into his lap. Then he put his hand in his beard. Then the Prophet, may Allah bless him and grant him peace, opened his mouth and put his mouth in his mouth. Then he said, O Allah, I love him, so love him and the one who loves him!'""