Albert Barnes Commentary Numbers 23:10

"Who can count the dust of Jacob, Or number the fourth part of Israel? Let me die the death of the righteous, And let my last end be like his!" — Numbers 23:10 (ASV)

The fourth part of Israel—that is, each one of the four camps into which the host of Israel was divided (see Numbers 2), seemed to swarm with innumerable multitudes. Possibly Balaam could only see one camp. Balaam bears testimony in this verse to the fulfillment of the promises in Genesis 13:16; Genesis 28:14.

The righteous—that is, the ancestors of Israel, who died in faith, not having received the promises, but having seen them afar off (Hebrews 11:13). With their histories Balaam was familiar, particularly with that of Abraham, the righteous man whom God had raised up from the east (and) called to His foot (Isaiah 41:2).

Let my last end be like his—Render rather, “last estate,” for the reference is not so much to the act of death, as to all that followed upon it—to the future, in which the name and influence of the deceased person would be perpetuated.