What does Acts 13:20 mean?

Paul has shown the Jews in Pisidian Antioch how God saved the Israelites of Moses and Joshua's time by rescuing them from Egypt, refraining from judging them during the forty years in the wilderness, and defeating their enemies in the Promised Land (Acts 13:17–19). Genesis 15:13 and Exodus 12:40–41 apparently include 30 years when the Israelites were not afflicted. Those 370 years, in Egypt (plus 40 years in the wilderness (Numbers 32:13) and roughly 10 years entering the Promised Land (Joshua 19:51) add up to 450 years.

Paul's short comment here about the judges has several hundred years of history behind it. His audience is composed of Jews and God-fearing Gentiles who listen to the Hebrew Scriptures every week. They know that for several hundred years God saved His people from enemy forces using people referred to as "judges." God commissioned Samson, Gideon, Deborah and the rest to defeat Amorites, Moabites, and especially the Philistines.

The synagogue members also know the rhythm of the era of the judges. The people would reject God and worship foreign idols. God would judge them by allowing other nations to subjugate them. The people would cry out for deliverance, and God would send a judge to save them. Samuel was the last of the judges; after him came the time of the kings.

The first part of Paul's message covers God's saving work in the nation of Israel (Acts 13:16–25). The next four speak about the offer of salvation God gives through Jesus (Acts 13:26–41). Like the Israelites of the time of the judges, we must recognize and repent of our false worship and look to God for rescue. Some of Paul's audience accept this salvation; many don't.