Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Jer 28:1-9) A false prophet opposes Jeremiah.
(Jer 28:10-17) The false prophet warned of his approaching death.
Hananiah spoke a false prophecy. Here is not a word of good counsel urging the Jews to repent and return to God. He promises temporal mercies, in God's name, but makes no mention of the spiritual mercies which God always promised with earthly blessings. This was not the first time Jeremiah had prayed for the people, though he prophesied against them. He appeals to the event, to prove Hananiah's falsehood. The prophet who spake only of peace and prosperity, without adding that they must not by wilful sin stop God's favours, will be proved a false prophet. Those who do not declare the alarming as well as the encouraging parts of God's word, and call men to repentance, and faith, and holiness, tread in the steps of the false prophets. The gospel of Christ encourages men to do works meet for repentance, but gives no encouragement to continue in sin.
Hananiah is sentenced to die, and Jeremiah, when he has received direction from God, boldly tells him so; but not before he received that commission. Those have much to answer for, who tell sinners that they shall have peace, though they harden their hearts in contempt of God's word. The servant of God must be gentle to all men. He must give up even his right, and leave the Lord to plead his cause. Every attempt of ungodly men to make vain the purposes of God, will add to their miseries.