John Calvin on Jeremiah 51:12

These words seem to have been addressed to the Chaldeans rather than to the Medes or the Persians, as some expound them; for this is favored by the context; for as he bids them first to raise a standard on the walls, so he adds, Increase the watch, which refers to the citizens of Babylon, and then he says, set the watchmen All this cannot apply to the Persians and the Medes, but must be referred to the besieged, as being most suitable to them. I do not then doubt but that the Prophet here treats, with a taunt, all the efforts the Chaldeans would make for the defense of their city. For not only they who attack a city raise a standard, but also they who are besieged, and this as a sign of confidence, in order to show that they possess sufficient courage to check their enemies, and to sustain all their attacks. It was then the design of the Prophet to show, that however strenuously the Chaldeans might defend themselves, yet all their exertions would be in vain, because God would, without labor, destroy the city.

Raise, he says, the banner on the walls of Babylon, and strengthen, or increase the watch; and afterwards, set watchmen, so that every one might watch with more care than usual. He says at last, set in order the ambushes “When all things have been tried by you, your labor will be without any advantage, for the Lord hath spoken ” When the particle גם, gam, is repeated, it ought to be rendered as and so — for as the Lord hath thought, so will he do what he hath said, etc. He says again that God had thought, lest the faithful should imagine that he heedlessly casts forth threatenings; for this thought often occurs to the mind, that God terrifies without effecting anything, Hence the Prophet, that he might more fully confirm his prophecy, says, that the thing had been meditated upon by God; and we said yesterday that God does not deliberate with himself like men; but as we cannot otherwise understand the certainty and unchangeableness of his secret counsel, nor form an idea of the validity of his decrees, the word thought is mentioned. The Prophet, in short, means, that he brought forth nothing but what God had decreed. For words are often heedlessly uttered, and the reality and the words are not always connected; but Jeremiah testifies that he had taken what he announced from the hidden and immutable counsel of God. Then he adds, what he hath spoken or said; and this refers to his doctrine or his prediction. It follows, —

Jeremiah 51:13

13. O thou that dwellest upon many waters, abundant in treasures, thine end is come, and the measure of thy covetousness.

13. Quae habitas super aquas multas (vel, magnas,) quae multa es in thesauris, (id est, dives, vel, locuples) venit finis tuus, mensura cupiditatis tuae.