So shall my word be. God's word is creative. With the utterance the result is achieved. Hence the sublime passage, which even heathenism could admire (Longin; 'De Sublim.,' § 9), "And God said, Let there be light: and there was light" (Genesis 1:3).
Hence, too, the more general statement, "By the Word of the Lord were the heavens made; and all the host of them by the breath of his mouth" (Psalms 33:6; comp. Psalms 148:5). But it shall accomplish; rather, unless it has accomplished.
There is a mixture of two constructions, "It shall not return void," and "It shall not return unless it has accomplished," etc. It shall prosper. Every word that proceedeth out of the mouth of God has a prosperous course.
It is endued with life from God, and (as Delitzsch says) "runs like a swift messenger through nature and the world of man, there to melt the ice, as it were, and here to heal and to save; and it does not return from its course till it has given effect to the will of the Sender.
"The special "word" which the prophet has here in mind is the promise, so frequently given, of deliverance from Babylon and return in peace and joy to Palestine. But he carries his teaching beyond the immediate occasion, for the benefit of the people of God in all ages.