Charles Ellicott Commentary Deuteronomy 4:3

"Your eyes have seen what Jehovah did because of Baal-peor; for all the men that followed Baal-peor, Jehovah thy God hath destroyed them from the midst of thee." — Deuteronomy 4:3 (ASV)

Your eyes have seen. —Literally, your eyes are the ones that see — i.e., you are witnesses of these things. The men who perished by the plague because of the iniquity of Beth Peor—to the number of 24,000—seem to have been all members of the younger generation; for they had already passed the brook Zered. (See on Deuteronomy 2:13.)