Joshua 8:1-7

1 Then the Lord said to Joshua, Have no fear and do not be troubled: take with you all the fighting-men and go up against Ai: for I have given into your hands the king of Ai and his people and his town and his land:
2 And you are to do to Ai and its king as you did to Jericho and its king: but their goods and their cattle you may take for yourselves: let a secret force be stationed to make a surprise attack on the town from the back.
3 So Joshua and the fighting-men got ready to go up against Ai; and Joshua took thirty thousand men of war, and sent them out by night.
4 And he gave them their orders, saying, Go and take up your position secretly at the back of the town: do not go very far away, and let all of you be ready:
5 And I and all the people with me will come near the town, and when they come out against us as they did before, we will go in flight from them;
6 And they will come out after us, till we have got them away from the town; for they will say, They have gone in flight from us as before; so we will go in flight before them;
7 Then you will get up from your secret position and take the town, for the Lord your God will give it up into your hands.