The theology of Romans drives Paul to do what is reported in Acts. Paul’s ministry is all about the gospel, “which he promised beforehand through his prophets in the holy Scriptures, concerning his Son . . . the power of God for salvation to everyone who believes, to the Jew first, and also to the Greek” (1:1-2,16). In fact, four times in this first chapter, Paul specifically mentions “the gospel.”
Martin Luther was so influenced by Paul’s writing here – “For in it (the gospel) the righteousness of God is revealed from faith for faith, as it is written, ‘The righteous shall live by faith’” (1:17) – that he spoke out and the Protestant Reformation was born and its recovery of the gospel of grace.
So, why does Paul do what he does? Why does he endure beatings and hunger and mockings and imprisonment and shipwreck all that? He does what he does because men have suppressed the truth (1:18), because God is kind and patient and desiring that men come to repentance (1:4), because “by works of the law no human being will be justified” (3:20), because “all have sinned and fall short of the glory of God” (3:23), but also because the same will be “justified by his grace as a gift, through the redemption that is in Christ Jesus” (3:24)!
Even Abraham was saved by this gospel: “Abraham believed God, and it was counted to him as righteousness” (4:3). “Blessed are those whose lawless deeds are forgiven, and whose sins are covered; blessed is the man against whom the Lord will not count his sin” (4:8). Indeed!
How blest are they whose trespass
Has freely been forgiv'n,
Whose sins are wholly covered
Before the sight of heav'n.
Blest they to whom the Lord God
Does not impute their sin,
Who have a guileless spirit,
Whose heart is true within. –From Psalm 32