Jeremiah starts prophesying over Judah: Jeremiah 1–5:19

Jeremiah prophesied for more than 40 years, starting in the 13th year of Josiah’s reign, and continuing until after the fall of Jerusalem.

He was quite young when he was first called, with this word from God:

^1:5 I knew you before I formed you in your mother’s womb.
Before you were born I set you apart
and appointed you as my prophet to the nations.

In answer to Jeremiah’s concerns about his youth, God said:

^1:7 Don’t say, ‘I’m too young,’ for you must go wherever I send you and say whatever I tell you. And don’t be afraid of the people, for I will be with you and will protect you. I, the Lord, have spoken!

And to confirm the calling:

^{Jeremiah 1:9} Then the Lord reached out and touched my mouth and said,
‘Look, I have put my words in your mouth!
Today I appoint you to stand up
against nations and kingdoms.
Some you must uproot and tear down,
destroy and overthrow.
Others you must build up
and plant.’