Charles Ellicott Commentary Isaiah 55:11

"so shall my word be that goeth forth out of my mouth: it shall not return unto me void, but it shall accomplish that which I please, and it shall prosper in the thing whereto I sent it." — Isaiah 55:11 (ASV)

So shall my word be ... — The point of the comparison is that the predominance of fertility in the natural world, in spite of partial or apparent failures, is the pledge of a like triumph, in the long run, of the purposes of God for man’s good over man’s resistance. It does not exclude the partial, or even total, failure of many; it asserts that the saved are more than the lost. .