Jeremiah was called as a child: 'Before I formed thee in the bowels of thy mother, I knew thee: and before thou camest forth out of the womb, I sanctified thee, and made thee a prophet unto the nations' (Jer 1:5). He protested he was too young; the Lord touched his mouth.
For forty years — from the thirteenth year of King Josiah (c. 626 BC) through the destruction of Jerusalem (587 BC) and into the exile — he prophesied the coming Babylonian invasion, urged submission to Nebuchadnezzar as the will of the Lord, and was hated for it. He was beaten, imprisoned in stocks, cast into a muddy cistern, and rescued by the Ethiopian eunuch Ebed-melech. He saw the city fall and the Temple burned.
Forced down to Egypt with a remnant after the assassination of the governor Gedaliah, he prophesied there until his death. Tradition holds he was stoned to death at Tahpanhes. His Lamentations — five poems mourning the fall of Jerusalem — became the Office of Tenebrae in the Latin Triduum.
His prophecy of the New Covenant (Jer 31:31–34) — written 'on tablets of human hearts' — became the foundational text for the Christian understanding of the Eucharist and the indwelling Spirit.