Whoever does not show mercy will not be shown mercy

Abu Hurayrah (may Allah be pleased with him) informed that the Messenger (may Allah's peace and blessings be upon him) kissed Al-Hasan ibn ‘Ali while Al-Aqra‘ ibn Hābis At-Tamīmi was sitting with him. Al-Aqra‘ remarked: "I have ten children, and I have never kissed any of them." Thereupon, the Messenger (may Allah's peace and blessings be upon him) looked at him and said: "Whoever does not show mercy will not be shown mercy."

In another narration: "What can I do if Allah has removed mercy from your heart?" Meaning: If Allah, the Almighty, has taken the feeling of mercy away from your heart, can I ever bring it back?