Sahih Muslim Book 30, Hadith Number 5735.

Chapter : The mercy-and tenderness shown by Allah’s Apostle (may peace be upon him) towards children, members of his family. and his humility and his sublime qualities.

‘Aisha (Allah be pleased with her) reported that there came a few desert Arabs to Allah’s Messenger (may peace be upon him) and said: Do you kiss your children? He said: Yes. Thereupon they said: By Allah but we do not kiss our children. Thereupon Allah’s Messenger (may peace be upon him) said: Then what can I do if Allah has deprived you of mercy? Ibn Numair said: (We has deprived) your heart of mercy.