Shall command, i.e. shall by his sovereign and powerful providence give it, even when it seems furthest from thee, and not likely to come to time without a word of command from God himself.
Related Commentaries of Deuteronomy 28:8
Deuteronomy 28:8
8 The LORD shall command the blessing upon thee in thy storehouses,b and in all that thou settest thine hand unto; and he shall bless thee in the land which the LORD thy God giveth thee.