Gal. 2:19, For I through the law I died to the law, that I might live unto God. 20 I am crucified with Christ: nevertheless I live; yet not I, but Christ lives in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me. 21 I do not frustrate the grace of God: for if righteousness come by the law, then Christ is died in vain.
The wages of sin is death, and our sin required our death, but God so loved, that He stepped out of eternity into time in the person of Jesus, and died, not just for us, but as us, so that our sins penalty could be paid in Christ. He took us in His person to the place of execution, and justice was satisfied; but more than that, the sinner we were in our fallen condition, died on that Cross in His death, so that in union with His resurrection we now share His life as our life, so that we can now live a life of righteousness, supernaturally before God, and faith is the transport that lifts us out of the ruin of self effort into the realm of the life of Heaven Jesus lives in us.
Here is a fun quote, “Faith has one function. The function of faith is to lift out of the ruin; out of the ruined race, out of the ruined world -out of time back into eternity. It is to lift us out from here, from ourselves and what we are and what we are involved in, up on to the heavenly level.” As Christians all of are in Christ, and therefore Christ is in us, but faith allows us to abide up in that reality.