It's the simplest and best argument for OSAS (aside from its overwhelming Scriptural evidence) that I can think of.
Hebrews 7:12 says the Law has changed. So Jesus did not come to abrogate God's Eternal Moral Laws (like do not murder, do not hate, do not commit adultery, do not steal, etc.). Jesus nailed to the cross those ordinances that were against us (like the Saturday Sabbath, the death penalty for disobeying God's laws, circumcision, the dietary laws, etc.) (See Colossians 2:14-17). Jesus says, "Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill." (Matthew 5:17). So Jesus did not come to destroy all Law and it's consequences but He came to fulfill them into their true intended purpose with the commands given to us within the New Testament. These commands are based on love. Love God and love your neighbor.
But what about Paul condemning the idea of trying to be justified by the Law?
This would be the Old Covenant Law and not all law that Paul was condemning (For example: Paul condemned circumcision (Which was a part of the Old Law); See Romans 3:1, Galatians 2:3, Galatians 5:2, etc.).
But what about Ephesians 2:8-9 and Titus 3:5?
Well, Ephesians 2:8-9 and Titus 3:5 are talking about Initial Salvation (or Ultimate Salvation) (i.e. Justification) and they are not talking about Continued Salvation or Sanctification. The Bible also does teach about Sanctification and how it is also a part of the Salvation Process. To deny this is to deny the rest of Scripture. For James says, "Ye see then how that by works a man is justified, and not by faith only." (James 2:24). "Even so faith, if it hath not works, is dead, being alone." (James 2:17). Paul says, "They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate." (Titus 1:16). The author Hebrews says, "And being made perfect, he became the author of eternal salvation unto all them that obey him;" (Hebrews 5:9). But what about salvation being a gift thru grace? Well, a person is initially saved by God's grace and not of themselves when they first come to Christ. A person is ultimately saved by God's grace as a gift because if they sin, they can get clean thru repentance (i.e. confessing their sin - See 1 John 2:1, and 1 John 1:9) and not by going out and doing another good work. That is why salvation is ultimately a gift. However, people are confused as to what the gift actually is. The gift from God is Jesus Christ (2 Corinthians 9:15) (John 3:16). While Jesus can set us free by forgiving us of our past sins by His death and resurrection; Jesus also sets us free from being a slave to sin, too. For Jesus was manifested to destroy the works of the devil (1 John 3:8). Jesus will not only save a person initially by His work on the cross and by His resurrection, but Jesus can save a person from their life of sin, too. Regeneration is not a true regeneration if there is no spiritual transformation in a person's life.
Jesus is in the life changing business. For Jesus has fixed up broken homes (or familes). Jesus has drawn the alcoholic away from the bottle. Jesus has helped the gambler to put down his cards and walk away from the game. Jesus has helped the drug addict from the power of the needle. Jesus has helped the harlot from being a slave to sexual sin and money. For Jesus Christ changes lives. Jesus changed my life and He continues to change lives today (Making them new creations in His image).
"Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new."
(2 Corinthians 5:17).
Anyways, we know that Sanctification is also a process of salvation, because the Scriptures also say,
1 John 3:7 says, "let no man deceive you: he that does righteousness is righteous,"
1 John 1:7 says, "But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin."
1 John 3:8 says, "he that commits sin is of the devil"
John 3:20 says, "For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved."
Hebrews 10:26 says, "For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins."
1 John 2:3-6 says,
3 "And by this we know that we know him, if we keep his commandments.
4 He that says, I know him, and keeps not his commandments, is a liar, and the truth is not in him.
5 But whoever keeps his word, in him verily is the love of God perfected: by this we know that we are in him.
6 He that says he abides in him ought himself also so to walk, even as he walked."
1 John 5:12 says, "He that has the Son has life; and he that has not the Son of God has not life."
Romans 11:22 says, "Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off."
"....and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death." (Revelation 21:8).
"And cast the unprofitable servant into outer darkness: there shall be weeping and gnashing of teeth" (Matthew 25:30).
Hebrews 5:9 says, "And being made perfect, he became the author of eternal salvation unto all them that obey him."
Titus 1:16 says, "They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate."
He that rejecteth me, and receiveth not my words, hath one that judgeth him: the word that I have spoken, the same shall judge him in the last day. (John 12:48).
41 "The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity."
42 And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth."
(Matthew 13:41-42).
"And then will I profess unto them, I never knew you: depart from me, you that work iniquity."
(Matthew 7:23).
"Not every one that says unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that does the will of my Father [God] who is in heaven."
(Matthew 7:21).
"God's will is for you to be holy," (1 Thessalonians 4:3 NLT).
Without holiness no man shall see the Lord (Hebrews 12:14).
"26 And every one that hears these sayings of mine, and does them not, shall be likened unto a foolish man, who built his house upon the sand:
27 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it."
(Matthew 7:26-27).
7 Be not deceived; God is not mocked: for whatsoever a man sows, that shall he also reap.
8 For he that sows to his flesh shall of the flesh reap corruption; but he that sows to the Spirit shall of the Spirit reap life everlasting.
9 And let us not be weary in well doing: for in due season we shall reap, if we faint not.
(Galatians 6:7-9).
"If any speaks contrary to the words of Jesus Christ and the doctrine of Godliness, he is proud and he knows nothing"
(1 Timothy 6:3-4).
"God resisteth the proud, but giveth grace unto the humble."
(James 4:6).
"but if you will enter into life, keep the commandments."
(Matthew 19:17).
"If you love me, keep my commandments."
(John 14:15).
"He that loves not knows not God; for God is love."
(1 John 4:8).
"Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him." (1 John 3:15).
"In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother." (1 John 3:10).
