From Martin Luther, Commentary on Romans, trans. J. Theodore Mueller (Grand Rapids, MI: Zondervan, 1954), xv. 

But the Holy Ghost is not given except in, with, and by faith in Jesus Christ, as he says in the introduction; and faith does not come, save only through God’s Word or Gospel, which preaches Christ, that He is God’s Son and a man, has died and risen again for our sakes, as he says in chapters 3, 4, and 10 [of Romans]. [italics added]. 

Theologians will tell you that if you don’t understand that “for our sakes” in their particular traditions nuanced sense, you’re not really believing the true gospel.  I say she who repents and has faith in a Christ (i.e. messiah) who is God incarnate and died for us, and is risen, believes the basic gospel and is saved.  That simple.  Theologians tend to complicate the gospel.