Charles Ellicott Commentary Deuteronomy 4:15

"Take ye therefore good heed unto yourselves; for ye saw no manner of form on the day that Jehovah spake unto you in Horeb out of the midst of the fire." — Deuteronomy 4:15 (ASV)

You saw no manner of similitude. —The worship of the invisible Jehovah is here specially insisted on. The difficulty of learning to worship one whom we cannot see is, happily, one which our education does not enable us to realize in its relation to ancient Israel. All nations had their visible symbols of deity. Centuries afterwards the world described the followers of Christ as Atheists, because they had no visible God. It is especially recorded in praise of Moses that he endured as seeing Him who is invisible (Hebrews 11:27).