Al-Adab Al-Mufrad, Book 5, Hadith 8 (In-Book) ⓘ
Abu Hurayra said, "The Messenger of Allah, may Allah bless him and grant him peace, kissed Hasan ibn 'Ali while al-Aqra' ibn Habis at-Tamimi was sitting with him. Al-Aqra' observed, 'I have ten children and I have never kissed any of them.' The Messenger of Allah, may Allah bless him and grant him peace, looked at him and said, 'Whoever does not show mercy will not be shown mercy.'"
حَدَّثَنَا أَبُو الْيَمَانِ، قَالَ: أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ: حَدَّثَنَا أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، أَنَّ أَبَا هُرَيْرَةَ قَالَ: قَبَّلَ رَسُولُ اللهِ صلى الله عليه وسلم حَسَنَ بْنَ عَلِيٍّ وَعِنْدَهُ الأَقْرَعُ بْنُ حَابِسٍ التَّمِيمِيُّ جَالِسٌ، فَقَالَ الأَقْرَعُ: إِنَّ لِي عَشَرَةً مِنَ الْوَلَدِ مَا قَبَّلْتُ مِنْهُمْ أَحَدًا، فَنَظَرَ إِلَيْهِ رَسُولُ اللهِ صلى الله عليه وسلم ثُمَّ قَالَ: مَنْ لا يَرْحَمُ لا يُرْحَمُ.
also referenced under: Hadith 91 (Reference) & Book 5, Hadith 91 (English)