Tafsir of Ad-Dhariyat 51:21

(And in yourselves) meaning: in your own essences, there are signs; for there is nothing in the world but that there exists its counterpart within the human essence, which points—as the former does—to the Creator. This includes the unique, beneficial configurations, the astonishing appearances, the wondrous compositions, the capability for marvelous actions, the deduction of various crafts, and the gathering of diverse perfections. The signs within the self are too numerous to be counted.

It has been said: What is intended by this is the difference in languages, appearances, colors, and temperaments; this was narrated by 'Ata' from Ibn 'Abbas. It has also been said: It refers to the path of food and the path of drink. The truth is that there is no limit [to these signs].

(Do you not then see?) Meaning: Do you not look and perceive with the eye of insight? This is a reproach for abandoning the examination of the signs on the earth and within the self. It has been said that it refers to the latter.