The verse "Now Jeremiah came in and went out among the people; for they had not put him into prison," from Jeremiah 37:4, means that during this particular period, Jeremiah was relatively free. He wasn't under arrest or confined. He could interact with the people of Jerusalem, moving about the city without restrictions.

The key point is the last part of the verse: "for they had not put him into prison." This indicates that earlier or later in the book of Jeremiah, he would be imprisoned. It highlights a temporary respite in the persecution he faced for his prophetic messages.

Here's a breakdown of the implications:

Freedom of Movement: Jeremiah could continue his ministry, even though it was likely unpopular. He could speak to people, deliver God's messages, and try to warn them of the impending destruction.
Contrast with Later Imprisonment: The verse subtly prepares the reader for the difficulties and persecution Jeremiah will later endure. It emphasizes that his freedom was not a permanent state.
Contextual Significance: The context of Jeremiah 37 is important. The Babylonian army had temporarily withdrawn from Jerusalem (due to the Egyptians trying to relieve the city), which might have created a brief window of relative peace and lessened the immediate threat that caused his imprisonment. In this period, he was walking among the people. However, this freedom was short-lived as later in the chapter, he's arrested again.
Divine Providence: Some scholars interpret the verse as showing God's hand at work. God allowed Jeremiah this period of freedom to continue his mission of warning and repentance.

In short, this verse tells us that at this specific point in time, Jeremiah was free to move and speak among the people because he hadn't been imprisoned yet. This temporary freedom is contrasted with the imprisonment that comes later in the narrative.