The Israelites are not the only ones who know how to pull the wool over the eyes of their enemies!
In Joshua 9, the Gibeonites come up with a plan to save their skins. Although they live in a nearby city in the Promised Land that the Israelites are taking over, the Gibeonites pretend to be from far away. They even bring along moldy food and worn-out sandals to convince the Israelites that they had to journey for quite a distance to visit them.
The Gibeonites successfully persuade the leaders to make a peace treaty with them, on oath before God. Unfortunately for the Israelites, they took the Gibeonites' word for it instead of inquiring of the Lord.
When the trick was discovered, Joshua permitted the Gibeonites to live so as to keep the oath, but made them servants of the Israelite people. I guess it beats being destroyed!
Joshua 9 shows us that it is always right to go to the Lord with a question. The Israelites harmed their own cause by being foolish and rash with a vow that they did not pray about first.