But the leaders replied, “Since we have sworn an oath in the presence of the Lord, the God of Israel, we cannot touch them. This is what we must do. We must let them live, for divine anger would come upon us if we broke our oath. (Joshua 9:19–20).
The leaders of Israel were deceived. A nearby people came to the leaders and told them they had come from far away and asked to make a treaty with them. The Israelite leaders fell for the deception and didn't think to check with the Lord. When the rest of the people learned about the deception they were angry and the verses above were the response of the leaders.
Even though they were deceived a promise is a promise. God expects us to keep our promises. He is truth, and expects us to be people who speak truthfully to each other.
Perhaps you have been caught in a promise you probably shouldn't have made. Or maybe you have had someone promise you something and then broke their word. Truth matters. Lies, fake news, and empty promises abound. God's people must lead the way to going back to a time when a promise meant something.