Deuteronomy 4:15 - Ellicott's Commentary On The Whole Bible

Ye 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 realise in its relation to Israel of old. 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).