The Messenger of Allah ﷺ kissed Hasan bin Ali while Aqra bin Habis Tamimi was sitting with him.Aqra remarked, "I have ten children, and I have never kissed any of them."The Messenger of Allah ﷺ looked at him and then said, "Whoever shows no mercy will be shown no mercy."
قبل رسول الله ﷺ الحسن بن علي وعنده الأقرب بن حابس التميمي جالسا فقال الأقرع: إن لي عشرة من الولد ما قبلت منهم أحدا، فنظر إليه رسول الله ﷺ ثم قال: من لا يرحم لا يرحم
Bukhari narrated it in Al-Adab (5997) and Muslim in Al-Fadail (65:2318), both through Zuhri, who said, "Abu Salama bin Abdul-Rahman told us that Abu Hurairah said," and then he mentioned it.