As we saw last week: Original sin brings eternal death to those not born again through Baptism and the Holy Spirit.
A new birth alone - and nothing short of that - will save us. No medicine, no balm, no surgery; education cannot do it, nor can discipline, correction, coercion, coaxing; no law can help us to avoid or avert our impending doom. Yes, these things may help gain some external order – but there is no cure for sin here.
A new birth must take place; a new life must be created.
This new birth is the work of the Holy Spirit. He, and he alone, can produce & sustain a new life. "I believe that I cannot by my own thinking or choosing believe in Jesus Christ, my Lord, or come to him..."
But the Holy Spirit alone has done this work, through Word and Sacrament.