Did God tell Israel about Christ's death and grace when He gave the Law?
No. Scripture presents revelation as progressive: when God gave the Law, He did not reveal that Christ would one day die and bring grace to the world. Israel remained under the Law's burden for 1,500 years until the faith way and the doctrines of grace were later revealed.
Les explains that Scripture is a progressive revelation, meaning God did not tell everything up front. When He gave the Law, He did not tell Israel and the rest of the world that one day Christ would die and send the world grace. Instead, Israel went 1,500 years under the Law, which was a constant burden with no liberty and constant fear, even bringing death for something like picking up a stick on the Sabbath. They were kept shut up under that burden until the faith way was afterward revealed, and then progressively God revealed the tremendous doctrines of grace.