Paul taught "where sin abounds, grace much more abounds" and we have been justified "as a gift" (that is, as a FREE gift), so that God's forgiveness is unmerited. Grace, justification, sanctification, redemption, eternal life, and yes, even faith (the Biblical kind), are all the gift of God, and not from ourselves (
Eph. 2:8). He also taught that faith in Christ without any works still results in righteousness imputed:
Rom. 4:5 "But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness."
And to this, the Judaizers claimed that Paul taught antinomianism, in which Paul condemns them in
Rom. 3:8 "And why not
say (as we are slanderously reported and as some claim that we say), 'Let us do evil that good may come'? Their condemnation is just."
And even the apostle Peter admitted that some of Paul's writings were hard to understand, because it takes familiarity with scripture and spiritual mindedness to grasp it.
2 Pet. 3:15-16 "and regard the patience of our Lord as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you, as also in all his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the Scriptures, to their own destruction."