Charles Ellicott Commentary Deuteronomy 33:25

"Thy bars shall be iron and brass; And as thy days, so shall thy strength be." — Deuteronomy 33:25 (ASV)

Your shoes shall be iron and brass. —Perhaps we should rather read, your bars shall be iron and brass. The word here rendered “shoes” in the Authorised Version does not occur elsewhere. The nearest word to it means “locks” or “fastenings.” It is also uncertain whether the whole sentence belongs to the blessing of Asher, or to all Israel. It seems most likely that, as Asher’s territory was at the northern end of Palestine, close to the pass by which the most formidable invaders must enter, an assurance is given here that the frontier of Israel should be safe. “Iron” and “brass” are mentioned together in connection with gates and bars in Psalm 107:16; Isaiah 45:2. But they are not usually connected with “shoes” in the Old Testament.

And as your days, so shall your strength be. —The word for “strength” does not occur elsewhere in the Old Testament, but the Targums, the Septuagint, and other authorities seem to agree on its interpretation, and the form of the word points to this meaning, “strength,” so that there is little doubt about its correctness. But the meaning of the clause is variously given by Jewish authorities: “Your strength in old age shall be as the strength of your youth;” or, “As you spend your days (in doing the will of the Holy One or not), so shall your strength be.”