OF course a legalist CAN'T believe in OSAS.
It would make your legalism of no effect.
Better be careful and do all the do's and don't do the don't's or otherwise LOSE SALVATION. Its all part of the legalists mind-set.
But what does Faith say?
Faith says "My Sheep hear My Voice and I give them Eternal Life"
Faith says "I will Never leave you nor forsake you"
Yes, Never leave you or forsake you! Beautiful words!
But I see you did not answer regarding Revelations, and that is okay, but, if you do agree with Revelations then;
Rev_12:17 And the dragon was wroth with the woman, and went to make war with the remnant of her seed,
which keep the commandments of God, and have the testimony of Jesus Christ.
Rev_14:12 Here is the patience of the saints:
here are they that keep the commandments of God, and the faith of Jesus.
Rev_22:14
Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
These are impossible to reconcile with your position. The only way to maintain your position would be to agree with many who simply refute the book of Revelations.
I understand the refutation in light of the several contradictions to how many have interpreted Paul's words.
It is also harder to reconcile that a book (Revelations) that is written by John from the mouth of Jesus Himself some 30 years after the last epistle of Paul was written and never even mentioned or confirmed the doctrine of Grace. So that leaves us wondering why He wouldn't confirm a monumental change in the salvation doctrine you derive from Paul's words. I think Paul explains His own words, but most OSAS and "Cheap Grace" adherents deny Paul's own writings that bring that doctrine back in line with the rest of scripture. This was the reason for Peters warning;
2Pe 3:14-17 NIV So then, dear friends, since you are looking forward to this, make every effort to be found spotless, blameless and at peace with him. (15) Bear in mind that our Lord's patience means salvation, just as our dear brother Paul also wrote you with the wisdom that God gave him. (16) He writes the same way in all his letters, speaking in them of these matters. His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction. (17) Therefore, dear friends, since you already know this, be on your guard so that you may not be carried away by the error of lawless men and fall from your secure position.
If you find Revelations hard to accept I say put that out there. If this is true for you don't you think we could all enter into discussion on this important matter?