Living by faith, not sight
Deut. 31:12: Assemble the people—men, women and children, and the aliens living in your towns—so they can listen and learn to fear the Lord your God and follow carefully all the words of this law (NIV).
Moses was very clear about the obligation of the Israelites to be people devoted to God's words, and he instructed the people to pass that knowledge down from parents to children. Although the God of Israel could not be seen, He spoke through His Word. In contrast, the people of the nations surrounding the Israelites worshipped man-made idols that could be seen, but could not speak, because they were lifeless.
Moses warned the people about turning away from the words of the living God and worshipping dead idols. He knew that they were inclined to worship by sight, rather than by faith. As we know, the Israelites did turn and worship other gods, and God used the Assyrian and Babylonian armies to discipline them.
Like the Israelites, we are presented with a choice each and every day. Will we live by faith in that which is unseen or chase after the lifeless idols of earthly success?
When we worship material things, we are living by sight and not by faith.