Paul informed them that God would forgive their sins if they believed in Jesus.

Acts 13:38-41

38-39 38-39“Therefore, my fellow Israelis and other friends, it is important for you to know that we(exc) are declaring to you that God can forgive you for your sins as a result of what Jesus has done. Because of what Jesus has done, God considers that everyone who believes in Jesus is no longer guilty (OR, the record has been erased {God has erased the record}) concerning everything that they have done that displeased God. But when God does that for you, it is not as a result of your obeying the laws that Moses wrote. 40 Therefore be careful that God does not judge you [MTY], as one of the prophets said [MTY] that God would do! 41 The prophet wrote that God said,

You who ridicule me, you will certainly be astonished when you see what I am doing, and then you will be destroyed. You will be astonished because I will do something terrible to you while you are living. You would not believe that I would do that even though someone told you!”