Isaiah 43:18-20 (NIV) says this “Forget the former things, do not dwell on the past. See I am doing a new thing! Now it springs up; do you not perceive it? I am making away in the desert and streams in the wasteland.”
In the context of this, God through the prophet Isaiah spends about 30 chapters warning Israel (and others) of the coming judgment for their rejection of God. But in Chapter 40 we see a turn that God will bring bring comfort and restore them, through the coming of the Messiah.
After Israel outright rejected their God and worshiped other Gods, he offers them renewal in the Messiah. “Forget the former things, do not dwell on the past.” God forgets their sin – but it’s not a human forgetfulness (like”I lost my wallet”) it’s a divine all-knowing grace-drenched forgetting. (Like “I know everything, and I intentionally am not remembering it.”) He isn’t going to dwell on their sins – why? Because the Messiah will absorb the wrath and penalty for all sin. He calls them to focus on the new thing he is doing, not the old. Forget that, he says!
We can apply this to us in the sense that we are of the new covenant in Jesus. Jesus is the Messiah, the one whom God himself provided as light and life, and the one who settles the past (and present, and future) sins through his righteous life, the shedding of his divine blood on the cross, and his resurrection — the GOSPEL! When we are given a new life in Jesus we are also called to forget the past, don’t dwell on the past and instead intentionally focus on the growing life life in Jesus that is “springing up” in us. It’s there, “do you not perceive it?”
When life happens, and there is seemingly no path forward, he creates one. He “makes a way in the desert and stream in the wasteland/wilderness.” We are created by God to glorify Him in every area of our lives (jump back a few verses to v7), God provided the ultimate way for us to do this in Jesus the Messiah and he promises to make a way forward for us to that today.