John Wesley on 1 Chronicles 15:23

Door - keepers - They were appointed to keep the door of the tent in which the ark was to be kept, that no unallowed person might press in and touch it; and in like manner they were to attend upon the ark in the way, and to guard it from the press and touch of prophane hands; for which end these two went before the ark, is their other two brethren mentioned in the close of ver.24, came after it.