I’ve read and heard many times… “I am the same yesterday, today and tomorrow.” Recently though I’ve been digging into Old Testament and came across Nahum and then Habakkuk. It’s hard to understand the quote noted above about “I am the same…” and apply that to some of the Old Testament books as they speak of a God who is unforgiving and full of wrath. Can you please shed some light there for me? For a younger Christian, it appears we read about 2 completely different versions of God from the Old to the New Testaments. I realize that’s not the case as God doesn’t contradict Himself so I’m just working to understand.
If you’re thinking of Hebrews 13:8 the passage actually says Jesus Christ is the same, yesterday, today, and forever. But to answer your question, the difference between the Old Covenant and the New is the cross. Paul explained this in Colossians 1:19-20 saying in effect that because the Lord’s death took care of the sin problem, God was able to reconcile Himself to all things and make peace with His creation.
So it’s not that God has changed. He still demands a sin-free life from everyone. We who believe that with His death the Lord has paid the full penalty due us for our sins benefit by no longer being accountable for the penalty ourselves. God benefits by being able to see us as if we had never sinned at all.