It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: When Allah Almighty created the earth, it began to sway, so Allah Almighty created the mountains and anchored them upon it, and thus it became stable. The angels were greatly astonished at the creation of the mountains, so they said: O Lord! Is there anything among Your creation that is harder than the mountains? Allah Almighty said: Yes, iron is harder. They said: O Lord! Is there anything among Your creation that is harder than iron? He said: Yes, fire is harder. They said: O Lord! Is there anything among Your creation that is harder than fire? He said: Yes, water is harder. They said: O Lord! Is there anything among Your creation that is harder than water? He said: Yes, wind is harder. They said: O Lord! Is there anything among Your creation that is harder than wind? He said: Yes, the son of Adam who gives charity with his right hand and conceals it from his left hand.