"So the Israelites set out and on the third day came to their cities: Gibeon, Kephirah, Beeroth and Kiriath Jearim. But the Israelites did not attack them, because the leaders of the assembly had sworn an oath to them by the Lord, the God of Israel. The whole assembly grumbled against the leaders, but all the leaders answered, 'We have given them our oath by the Lord, the God of Israel, and we cannot touch them now.'" NIV translation
The Israelites went to confront the Gibeonites but did not attack them because of the treaty. The rest of the people were upset with the leadership but they could not break their oath. This is a reminder of what happens in any group that is not completely led by God.
This would have been a total of six days after they had made the decision. We are reminded that the number six is associated with the works of men and, now, they had come to the end of what they could do. We are reminded that they could have avoided all of this by praying on that first day. It is also better for us if we do not swear any oaths because the devil can use them against us.