He said, No; but [as] prince of the host of Yahweh am I now come. Joshua fell on his face to the earth, and did worship, and said to him, What says my lord to his servant?
So this is the first Passover in the Promised Land. They came in just four days beforehand, circumcised themselves, and now are beginning this new relationship with God observing the Passover now in the new land.