Here’s a great answer from Sandy Richter.
Is understanding the context of the Old Testament essential to understanding the meaning of what Jesus taught?
I certainly believe with all the campus ministries and Four Spiritual Laws and tracts … the simplest presentation of the Gospel message can bring someone into the Kingdom–but … that is just the tip of the iceberg. Who Jesus was, the message he came to bring, the promise he came to fulfill, the lineage that he comes as the final representative–all of these things are Old Testament messages.
I often will joke with my students that if you want to, you can listen to your favorite album on a cheap, one-speaker AM radio, or you can listen to it on Dolby surround sound. Make your choice. You can have one three-step presentation of the Roman Road, or you can come to realize that the last Adam of 1 Corinthians is the typological representation of the first Adam that stood in the Garden, and that the reason Jesus needs to be tempted by Satan in the wilderness is because the first Adam was tempted by Satan; the first Adam failed the test, and the second Adam didn’t.
When Jesus stands on the mountain and declares a new law, he’s not coming up with a new idea–he’s standing on the mountain like Moses did and declaring to a new people, “I am the new lawgiver.” When he breaks his bread at communion meal, he calls himself the new Passover and tells his people, “I’ll put my blood on the lintels of your house and the death angel will pass over.” All of these messages are as old as the hills. We truncate them into this one final expression, and I think it cheapens the message.