God in this verse briefly reminds his servant, that though he would be supplied with invincible power, yet he would have great trials, so that his office would not be, according to a common saying, a mere play. He then shews for what purpose he would be made like a fortified city, an iron pillar, and a brazen wall, even that he might manfully fight, and not for the purpose of keeping away all dangers, and all fightings, and everything hard and grievous to the flesh. We, in short, see that the promise was given for this end, -- that Jeremiah, relying on God's aid, might not hesitate to set himself against all the Jews, and that whatever might be their fury, he might still be courageous.

Now a profitable doctrine may be hence gathered, even this -- that whenever God promises his servants victory over their enemies, they ought not to make this the occasion of fostering their torpidity or idleness, but, on the contrary, of gathering courage, so that they may proceed boldly and unweariedly in the course of their vocation. In short, God promises to be their deliverer, but at the same time exhorts them to resist all the assaults of their enemies.

Hence he says, They shall fight with thee, but they shall not prevail, for I am with thee to deliver thee. ¹ From these words we see that Jeremiah was fully armed, that he might not fear on seeing dangers surrounding him; for God does not here declare that he would be like a wall to him to prevent him from being assaulted, but he says that he would deliver him; as though he had said, "Prepare thyself to suffer; for except I were thy deliverer, it would be all over with thee, and thou mightest perish a hundred times; but there is no reason for thee to fear any dangers amidst thousand deaths, since I am present with thee as thy deliverer." Now follows --