Whoever does not have mercy, would not be given any mercy
From Abu Huraira, who said: "The Messenger of Allah (Sallahu Alaihee Wasallam) kissed Hasan bin A'lee and Al-Aqra' bin Haabis At-Tameemee was sitting with him. So Al-Aqra' said: "Indeed I have 10 children and I have not kissed any of them." So the Messenger of Allah looked at him and said: "Whoever does not have mercy, would not be given any mercy." Authentic Hadith, narrated by Al-Bukhaaree and Muslim. Shaykh Abdur-Razaaq (may Allah protect him) went onto explain: This Hadith explains the fact that it is from Rahmah (Mercy) to kiss one's children. It is also a sign of affection and kindness towards them.