Jamieson, Fausset and Brown on Jeremiah 26:16

16. princes ... all the people--The fickle people, as they were previously influenced by the priests to clamor for his death (Jr 26:8), so now under the princes' influence require that he shall not be put to death. Compare as to Jesus, Jeremiah's antitype, the hosannas of the multitude a few days before the same people, persuaded by the priests as in this case, cried, Away with Him, crucify Him (Mt 21:1-11; 27:20-25). The priests, through envy of his holy zeal, were more his enemies than the princes, whose office was more secular than religious. A prophet could not legally be put to death unless he prophesied in the name of other gods (therefore, they say, "in the name of the Lord"), or after his prophecy had failed in its accomplishment. Meanwhile, if he foretold calamity, he might be imprisoned. Compare Micaiah's case (1Ki 22:1-28).