How long did Israel go under the Law before the doctrines of grace were revealed?
Israel went 1,500 years under the Law before the doctrines of grace were progressively revealed. The Law was a constant burden, keeping Israel shut up until the faith that should afterward be revealed. Scripture presents this as progressive revelation, not something God disclosed all at once.
Les teaches that Israel went 1,500 years under the Law before God progressively revealed the tremendous doctrines of grace. The Law was a burden resting on the people's shoulders, and those under it knew nothing of liberty, only constant fear, because violations such as picking up a stick on the Sabbath brought death. Israel was under that burden constantly, 24 hours a day, and was kept shut up under it until the faith which should afterwards be revealed. Les explains that Scripture is a progressive revelation; God did not tell everything up front, and when He gave the Law He did not tell Israel and the rest of the world that Christ would one day die and send grace. So after those 1,500 years, He progressively revealed the doctrines of grace.