Why does Genesis 12:1 say 'Now the Lord had said' instead of just 'the Lord said'?
The phrase points back to an earlier command. Genesis 12:1 uses 'had said' because the Lord had already spoken to Abraham back in chapter 11, telling him to leave his country, his kindred, and his father's house for a land God would show him. Chapter 12 records the covenant after that prior instruction.
Les teaches that in Genesis 12:1 the words 'Now the Lord had said' reach back to Genesis chapter 11. The command to get out of his country, from his kindred, and from his father's house, unto a land that God would show him, had already been given. Genesis 12 then presents the Abrahamic covenant: God promises to make of Abraham a great nation, bless him, make his name great, bless those who bless him, curse him who curses him, and bless all families of the earth in him. Les points out that God has not changed His mind; the Abrahamic covenant is still valid and still going to be fulfilled. It was the whole idea of Christ's first coming to fulfill these promises made to Abraham, Isaac, and Jacob, though Israel rejected it and crucified their Messiah. God set them aside and blinded them, but He has not taken them out of His program; He will come back and finish the Abrahamic covenant.
Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father’s house, unto a land that I will shew thee: