The commander of the Lord’s army replied, “Take off your sandals, for the place where you are standing is holy.” And Joshua did as he was told. Joshua 5:15 (NLT)
Joshua was facing a new season of his leadership when he encountered the Commander of the Lord's army. He was told to take off his sandals as he was standing on holy ground. It was holy because God was there. That was the time when God gave Joshua new instructions for the conquest of the Promised Land.