Charles Ellicott Commentary Psalms 72:9

"They that dwell in the wilderness shall bow before him; And his enemies shall lick the dust." — Psalms 72:9 (ASV)

They that dwell in the wilderness...—The Hebrew word in other places is used of “wild animals” (Psalms 74:14; Isaiah 23:13). Here apparently it refers to the nomad tribes wandering over the desert. The Septuagint and ancient versions generally have “Ethiopians.”

Lick the dust.—The allusion is to the Eastern etiquette of prostration before a sovereign.