Joshua 9

Then the men of Israel took some of their provisions; but they did not ask counsel of the Lord.  So Joshua made peace with them, and made a covenant with them to let them live; and the rulers of the congregation swore to them.vv.14-15

Read chapter 9
Deception comes even in the "good times."  Joshua and all of Israel are feared by the nations for the rumor throughout the surrounding nations of what their God had done for them.  So because of this fear of the God of Israel men from Gibeon disguise themselves so that they can make a treaty with Israel under a different reason that will ultimately save them even when they are found out who they really are.  The leaders of Israel are curious and ask questions, yet Joshua and the leaders ultimately trust in their own discernment than even to think to ask the Lord, as it seemed probably so innocent to them.  Yet it is noted this is clearly the mistake they made: "they did not ask counsel of the Lord."  So it's revealed only three days later who they really are and because of the covenant made with them and their honor to it so that the vow they made with God as their witness, the Gibeonites are spared from being destroyed.  They were to live but as slaves to Israel as a curse of their deception.  When do you find yourself making decisions without asking the Lord for wisdom and end up being deceived or regretful of not seeking the Lord first?