In case you want to ponder it some more, here's the story I shared of Keller's time 40 years ago in R.C. Sproul's living room listening to Old Testament scholar Alec Motyer. Sproul asked Motyer to share something about the connection between the Old Testament and the New. Here's one of the things he said:
Think about what an Israelite would say on the way to Canaan having come out of the Red Sea. Here’s what an Israelite would say. If you said “Who are you?”, he would say, “I was in a foreign land under the sentence of death, in bondage, but I took shelter under the blood of the Lamb, and our mediator led us out and we crossed over, and now we are on our way to the promised land but we are not there yet. But he’s given us his law to make us a community, and he’s given us the tabernacle because you have to live by grace and forgiveness. And his presence is in our midst and he’s going to stay with us until we get home.