Jeremiah 6:27

I have set thee for a tower and a fortress among my people, that thou mayest know and try their way.

God set Jeremiah as a tower and a fortress among His people in Judah. He was appointed as a watchful, testing presence placed in their midst to know and examine their way and conduct. In that office he served as a steadfast watchman and a strong defense, discerning the moral state of the nation.

As that fortress he was to stand firm against those who opposed him. God promised to be with him and to deliver him from his enemies. The examination he carried out exposed the people's way as corrupt, for they proved rebellious and slanderous. In the outcome of that testing they were shown to be like rejected, worthless silver.