Jeremiah 7 is a part of the Bible that talks about how the people of Israel were not following God's teachings and were instead doing bad things like stealing, lying, and hurting others. God was upset with them and wanted them to stop doing these things and start being good.
In the chapter, Jeremiah talks to the people and tells them that just going to the temple and offering sacrifices is not enough to make up for their bad actions. They need to change their ways and start doing what God wants them to do.
Think of it like this: Imagine you did something bad, like taking a toy from your friend without asking. If you just say sorry but keep on doing it, it doesn't really make things right. You need to stop taking their toys without asking and start being a good friend to them. That's what God wants the people of Israel to do too.