It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that once Uyaina bin Hisn came to the service of the Prophet (peace and blessings be upon him). He saw that the Prophet (peace and blessings be upon him) was kissing one of the two grandsons, Hasan or Husain (may Allah be pleased with them). He said, "O Messenger of Allah! You kiss them, whereas I have ten sons, but I have not kissed any of them?" The Prophet (peace and blessings be upon him) said: "He who does not show mercy to others, mercy is not shown to him."