"'For twenty-three years [...] the word of the LORD has come to me, and I have spoken persistently to you, but you have not listened'" (Jeremiah 25:3).
Jeremiah undergoes much behind-the-scenes character growth in his book. When we are introduced to him, he is a frightened young man who isn't too keen on this overwhelming task God is calling him to. God doesn't let him get away, though, and he begins to proclaim the words God has given him.
Fast-forward twenty-three years, and Jeremiah's still at it, warning the people of Judah what is coming if they don't repent and urging them to turn back to God while there's still time. He knows there's not much chance they'll listen; God as good as told him so multiple times. But the words of God burn on his lips, and he must speak them. Even if no one responds, still he must speak.
How did that scared boy become this bold man who spoke the unpopular truth and didn't care what his hearers thought of him? Where did that kind of courage come from?
At the beginning of Jeremiah's ministry, God had promised that He would be with him, delivering him from his enemies. His job was dangerous; God was well aware of that. He was sending Jeremiah to do a mission that would probably cost him his life. But God would be with him through it all.
It was his certainty in God's faithfulness that gave Jeremiah the boldness to keep speaking, even when by all human standards he was failing. For over two decades he had preached, and yet no one listened. No one cared.
But this was what God had called him to do, and he continued to do it with what can only be described as sheer stubbornness. He was faithful even if no one else was. And God gave him the strength to continue being so.