Many protestant errors on “faith alone,” and their misreadings of Paul, stem from the failure to distinguish between:
(1) Our reception of the gift of the Holy Spirit (by faith, no works); and
(2) New Covenant life IN the Spirit (duty to work, consequences for not).
These are two fundamentally different things.
The first is what Scripture, and Paul (most often) says about the inability of spiritually dead human nature to please God without regeneration, renewal, and rebirth by the Spirit.
—“Now when they heard this they…said to Peter and the rest of the apostles, ‘Brethren, what shall we do?’ And Peter said to them, ‘Repent, and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins; and you shall receive the gift of the Holy Spirit’” (Acts 2:37-38).
—“Hope does not disappoint us, because God’s love has been poured into our hearts through the Holy Spirit which has been given to us” (Rom. 5:5).
—“For neither circumcision counts for anything, nor uncircumcision, but a new creation [by the Spirit]” (Gal. 6:15).
—“And you he made alive, when you were dead through the trespasses and sins” (Eph. 2:1).
—“He saved us, not because of deeds done by us in righteousness, but in virtue of his own mercy, by the washing of regeneration and renewal in the Holy Spirit” (Tit. 3:5).
—“Let me ask you only this: Did you receive the Spirit by works of the law, or by hearing with faith?…Does he who supplies the Spirit to you and works miracles among you do so by works of the law, or by hearing with faith?” (Gal. 3:2, 5).
Etc.
The second is what Paul says about spiritually alive (born again) human nature that has received the Spirit, and is therefore capable of loving, obeying, and working according to Christ’s commands. That means it can disobey too, with eternal consequences.
—“For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body you will live” (Rom. 8:13).
—“For God did not give us a spirit of timidity but a spirit of power and love and self-control” (2 Tim. 1:7).
—“I can do all things in him who strengthens me” (Phil. 4:13).
—“Therefore, if any one is in Christ, he is a new creation; the old has passed away, behold, the new has come” (2 Cor. 5:17).
—“Do not be deceived; God is not mocked, for whatever a man sows, that he will also reap. For he who sows to his own flesh will from the flesh reap corruption; but he who sows to the Spirit will from the Spirit reap eternal life” (Gal. 6:7-8).
Etc.
This is all crystal clear in Jesus’s parables as well. Many involve servants of one kind or another receiving a free gift for which they did nothing, but then being expected to produce a return for the Master. The servants are all called by the Master and employed by Him. They are Christians. Those who produced a return were welcomed into Heaven. Those who didn’t were condemned to Hell.
All were made servants of the Master through no works of their own, but according to the Master’s mercy, lest any boast. But once made a servant, the Master expected a return; a harvest; fruit. If He didn’t get it, they were punished.
That is how salvation is both by faith without works (being spiritually dead, then born again by the Spirit through faith with no works of our own), and also by works (understood to be done by and with the Spirit who dwells in us and makes us a Temple). In other words, our works done without the Spirit are filthy rags, dead, and worthless. Our works done with the Spirit are truly good, pleasing, and meritorious—entirely thanks to God’s grace, which is the source of all their merit. Hence Paul’s constant exhortation TO CHRISTIANS to live and sow according to the Spirit so that we reap life, and his warning that failing to do so will reap death.
The Church Fathers completely clarified this for me. Once they did, so many passages in Scripture I simply couldn’t make sense of as a protestant suddenly made all the sense in the world.