“But the Israelites did not attack the towns, for the Israelite leaders had made a vow to them in the name of the Lord, the God of Israel. The people of Israel grumbled against their leaders because of the treaty. But the leaders replied, “Since we have sworn an oath in the presence of the Lord, the God of Israel, we cannot touch them.”
‭‭- Joshua‬ ‭9‬:‭18‬-‭19‬ ‭NLT‬‬

Not that what they did was right, but you got to hand it to them, at least the Gibeonites put in the effort to try to save themselves rather than give up. Israel definitely made a mistake here in not consulting God. The passage makes this very clear. We should be very careful when making vows. Vows should never be broken.

“A man who makes a vow to the Lord or makes a pledge under oath must never break it. He must do exactly what he said he would do.”
‭‭- Numbers‬ ‭30‬:‭2‬ ‭NLT

We should consult the lord in all that we do. This is even more important with vows. Since vows should never be broken, we need to be sure that we don’t pledge ourselves to something really bad, or even worse, break that pledge/vow. Be careful with what you say and promise.