Where can you trace the doctrine of the remnant in the Bible?

Les explains that the doctrine of the remnant can be traced from Genesis to Revelation, and it is all the way through Scripture. God has always kept a remnant. Christ promoted this beautifully in His earthly ministry with the analogy of the wide way, the broad way, and the narrow way: the mass of humanity goes down the broad way, but the remnant takes the narrow way. Paul goes on to say that in this age of grace, which is predominantly Gentile with some Jewish exceptions, there is a remnant of Jews who have become believers of the gospel of grace, a remnant according to the election of grace, not of law or Judaism. Les also notes that even as Elijah was shown there were 7,000 who had not fallen to idolatry, so today there is a remnant of Jews who recognize the very gospel of grace and the election of grace. He mentions reading a book of testimonies of Jews who became believers of this grace gospel, and though they are a remnant and very few can believe it, they are there.