Matthew Poole and continuators on Jeremiah 28:9

9 The prophet which prophesieth of peace , when the word of the prophet shall come to pass, then shall the prophet be known that the LORD hath truly sent him .

by Peace is here meant Prosperity, all good, being by the Hebrewes usually understood under the notion of Peace. The Prophets either prophesied evil or good, according as God revealed his will unto them; what way was for them to discover whether the Prophets were truly sent of God yea or no?

It was known by the Event, this was the Rule God set Deut. 18.22. When a Prophet speaketh in the name of the Lord, if the thing follow not, nor come to pass, that is the thing which the Lord hath not spoken. But this was not true on the contrary part, for a Prophet might speak a thing, which thing might come to pass, and yet he be none of the Lords Prophets, nor to be hearkned to, as appeareth from Deut. 13.1, 2. Some have thought, that Prophecyes concerning good things alwayes were brought to pass if the Prophet were a true Prophet, but it appeareth otherwise from chap. 18.9, 10. Prophecies both concerning good and evil, might not come to pass, and yet the Prophet be a true Prophet, in case the manners of the people altered, for in all promises or threatnings of temporal good or evil, there is a condition to be understood, God neither by his promises bindeth himself to do good to wicked men, nor by his threatnings tyeth up his own hands from shewing mercy to such as turn good, but some observe yet this difference, that good things are in Scripture never absolutely promised, but they come certainly to pass, and are fulfilled, but God for terrour often threatneth evil things, without expressing any condition, when notwithstanding a condition is understood, upon the fulfilling of which the threatning cometh not to pass, as it was in the case of Niniveh, upon the prophesie of Ionah. But the greater difficulty is to determine by what rule they could judge one a true or false Prophet, if they might not alwayes judge by the event, the coming, or not coming to pass of what he prophesied. I answer, they were to judge from the word of God, as well as from the Event. Isaiah 8.20. therefore Deut. 13.1, 2. the people were commanded not to hearken to that Prophet, which should confirm what he said by a sign or wonder, if his scope were by it to perswade people to Idolatry. So that if a Prophet prophesied good, and prosperity to any people, the people were to consider what his scope was, and whether what he prophesied was according to the Law of God, which speaketh no good to a wicked impenitent people, and though what he said came to pass, yet he was to be determined no true Prophet, if what he said were contrary to Gods revealed will, or his scope in speaking of it was to harden people in sinful courses, or to seduce them from the right wayes of God. Ieremiah here, as to the tryal of the truth of his, and Hananiahs contrary prophesies appealeth to the Event, telling him, that he as a man, heartily wished that his words might prove true.