Joshua 5:13-15

Now when Joshua was by Jericho, he looked up, and behold, a man was standing opposite him with his drawn sword in his hand, and Joshua went to him and said to him, “Are you for us or for our adversaries?” He said, “No; rather I have come now as captain of the army of the LORD.” Then Joshua fell with his face toward the earth and bowed down, and said to him, “What does my lord have to say to his servant?” The captain of the LORD’S army said to Joshua, “Remove your sandals from your feet, because the place where you are standing is holy (set apart to the LORD).” And Joshua did so. [Ex 3:5]