Like many of the prophets, when called Jeremiah is reluctant to play this role. But he is told by Hashem that even when in the womb this was his destiny. Jeremiah doesn’t know what to speak but Hashem stretches out his hand (yes anthropomorphic) and places words in Jeremiah’s mouth to both uproot corruption and plant health.
He has two visions: one is of the quick blossoming olive branch which is a warning that Hashem is quick to punish the wicked for their misguided behavior. Of course, Hashem’s speed may not be ours! And the second vision is of a boiling pot from which will emerge the invaders. This prophetic image warned of the Babylonians who would soon lay siege to Jerusalem and conquer it. But in the future, you will be like a fortified wall against enemies. So, Jeremiah even in these bad times is encouraged to tell the ear of the people that Hashem extends lovingkindness in the midst of troubles.