Albert Barnes Commentary Deuteronomy 33:29

"Happy art thou, O Israel: Who is like unto thee, a people saved by Jehovah, The shield of thy help, And the sword of thy excellency! And thine enemies shall submit themselves unto thee; And thou shalt tread upon their high places." — Deuteronomy 33:29 (ASV)

Be found liars unto thee - Perhaps rather, “cringe before thee.” The verb means to show a feigned or forced obedience: see the marginal references.

Tread upon their high places - that is, occupy the commanding positions in their land, and so have it in subjection.