Jami` at-Tirmidhi 1911
جامع الترمذي#1911SahihAbu Hurairah narrated:"Al-Aqra' bin Habis saw the prophet kissing Al-Hasan"- Ibn Abi 'Umar (one of the narrators) said:"Al-Hasan and Al-Husain." So he said: 'I have ten children and I do not kiss any one of them.' So the Messenger of Allah said: 'Whoever shows no mercy, he will be shown no mercy
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 27:17