To the churches in Galatia:
3 Grace and peace to you from God our Father and the Lord Jesus Christ, 4 who gave himself for our sins to rescue us from the present evil age, according to the will of our God and Father, 5 to whom be glory for ever and ever. Amen.
Substitutionary atonement is the big five-dollar phrase that comes to mind here, that Jesus suffered and died on the cross taking our punishment for us. That's a large part of the core of Christian thought, that Jesus died for our sins, becoming the sacrifice to end them all. That's the Good Friday part of the equation; the Easter part is that he rose again and is with God to this day.
The other interesting part of this passage is the "present evil age" part; we normally think of our modern culture is the near-pinnacle of evil compared to the past, but our modern culture at least has a veneer of the Gospel informing it. The same couldn't quite be said of the first century Roman empire. We're still in an evil age, just one with its own vices.