Why were the Jews expected to believe and live by the Law and tabernacle worship?
The Jews were expected to believe and live by the Law and tabernacle worship because God had revealed them. What was once a secret was no longer hidden; the revealed things belonged to them, so they were responsible to believe and live by them.
Les explains that Moses was writing to the children of Israel, who had not received everything revealed at once. Once God laid out the Law, the tabernacle worship, the ritual, and the civil law, those things were no longer secret. Therefore, God expected the Jew to believe it and live by it. The principle is that secret things belong to the Lord, but the things He reveals belong to us, making us responsible to respond in faith and obedience.