‘A’isha (Allah be pleased with her) reported that there came a few desert Arabs to Allah’s Messenger (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 (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.
Sahih Muslim, Book 43, Hadith 85