Mishkat al-Masabih 1923

Anas reported God’s messenger as saying:

When God created the earth it began to oscillate, so He created the mountains, ordered them on to it, and it became steady. The angels marvelled at the strength of the mountains and asked their Lord whether there was anything in His creation stronger than the mountains, to which He replied that iron was stronger. They asked if anything in His creation was stronger than iron, and He replied that fire was. They asked if anything in His creation was stronger than fire and He replied that water was. They asked if anything in His creation was stronger than water and He replied that wind was. They asked if anything in His creation was stronger than wind and He replied, “Yes, the son of Adam who gives sadaqa with his right hand concealing it from his left.” Tirmidhi transmitted it, saying this is a gharib tradition.