John Calvin Commentary Jeremiah 20:11

"But Jehovah is with me as a mighty one [and] a terrible: therefore my persecutors shall stumble, and they shall not prevail; they shall be utterly put to shame, because they have not dealt wisely, even with an everlasting dishonor which shall never be forgotten." — Jeremiah 20:11 (ASV)

Here the Prophet sets up God’s aid against all the plots formed against him. So, though treacherous friends on one hand might try privately to entrap him, and open enemies on the other hand might publicly oppose him, he still did not doubt that God would be a sufficient protection for him. And we should act in exactly the same way whenever Satan stirs up the wicked against us to oppose us, either by secret schemes or by open cruelty; God alone must be, as they say, our bronze wall. But first, we must know that He stands on our side, for the power of God can do nothing to encourage us unless we are firmly persuaded of this truth: that He is on our side. And how this confidence can be obtained, we will soon see.

He says that his persecutors would fall, so that they would not prevail, but be ashamed. We see how many persecuted the holy man, and also with what weapons they were furnished; for they possessed great power and were also endowed with cunning and intrigues. But the Prophet was satisfied with the help of God alone and boldly concluded that they would fall, for it was inevitable that God would prove victorious. Whenever, then, we fight with the world, the devil, and his slaves, this should first come to our minds: that God stands on our side to defend our cause and to protect our safety. This being settled, we may then boldly defy both the schemes and the violence of all enemies, for it is inevitable that God will scatter, lay prostrate, overwhelm, and reduce to nothing all those who fight against Him.

He further says that their reproach would be perpetual, and would never come to oblivion. We have already seen that the Prophet was burdened with many reproaches; but whenever God allows His servants to be exposed to the curses of the wicked, He aids them in due time, and therefore we should fully expect that He will shortly dissipate such slanders, like mists. Just as God, according to what is said in Psalm 37:6, brings forth the innocence of the godly like the dawn, which appears in a moment while the earth seems buried in darkness, so the Prophet now says that, on the other hand, the reproach with which God will cover all the wicked will be perpetual.