He said that Jesus never taught justification by faith alone apart from the Law. I responded with this:
I think this is the crux of the argument, so let's consider this point.
John 14:6 Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
Jesus was asked the way to the Father and He didn't say, "Keep the law". On the flip side He said that Matthew 5:18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
So then, according to the law how do you "come unto the father"?
What is this "new and living way" that Hebrews talks about, that is a fulfillment of the law, that aligns with what Jesus said about no one coming unto the Father but by me?
According to the law you can only come unto the Father on the day of atonement, and you can only enter the Holy of Holies if you are the High Priest and you have the atoning blood of the sacrifice. Jesus is telling us that His blood is that sacrifice, He is the High Priest, He is the one that opened the curtain to the Holy of Holies with His death. That is the fulfillment of the law. The blood of Bulls and goats only lasted for a year, and ever since Jesus crucifixion is no longer effective (rabbinical records prove this, after the crucifixion the day of Atonement never resulted in the proof that the sacrifice was accepted).
This is what Paul is telling us, salvation is being able to come unto the Father, there is no way without us receiving the atoning sacrifice of Jesus.
Paul never disparages good works, he always condemns the works of the flesh, but the biggest deceit was that you could be saved by your good works. There is only one way according to the law to be forgiven of sins and that is with the shedding of blood, and the law testifies that the only blood accepted by God to forgive your sins is the blood of Jesus. That is Paul's message and that is also Jesus message.
In conclusion, justification by faith alone is not Paul's idea, it is written in the law clear as day, and Jesus knew it, John the Baptist knew it, and that is why he told us that Jesus was the lamb of God that takes away the sin of the world.