Tafsir of Ad-Dhariyat 51:20

And on the earth are signs for those who have faith with certainty. Allah says that there are signs on earth that testify to the might of the Creator and His boundless ability. These signs include what Allah placed on the earth, the various plants, animals, valleys, mountains, deserts, rivers and oceans. He also created mankind with different languages, colors, intentions and abilities, and a variety among them, differences in the power of understanding and comprehension, their deeds, and ultimately earning happiness or misery. Allah put every organ in their bodies in its rightful place where they most need it to be. So He said؛

وفي أنفسكم أفﻼ تبصرون