Albert Barnes Commentary Numbers 24:20

"And he looked on Amalek, and took up his parable, and said, Amalek was the first of the nations; But his latter end shall come to destruction." — Numbers 24:20 (ASV)

When he looked — that is, in spirit, as he saw the Star (Numbers 24:17).

Amalek was the first of the nations — Rather, is preeminent among the neighboring nations: compare the same expression in Amos 6:1. Hence, the force of the words “higher than Agag,” (Numbers 24:7) that is, than the king of this powerful nation (Exodus 17:8). This rank, due to the warlike prowess of the tribe, Balaam contrasts with its approaching downfall and extinction.