Here is a quote from someone commenting on 1 John 3:9 in defense of OSAS theology: “Outwardly one can sin, but their soul doesn’t sin. That’s why they cannot sin; their inner being does not sin.”
This is the kind of conclusion that a person comes to based on eisegesis (interpreting a text or portion of text in such a way that the process introduces one’s own presuppositions,) rather than exegesis (interpreting the text based on the context).
The explanation above “outwardly one can sin, but their soul doesn’t sin” is a mystical belief and nowhere in the flow of thought in 1 John.
The words, commit sin, actually means habitually practices sin. Other good translations of the Bible, such as the Amplified Bible, bear this out, as well as a thorough reading of 1 John.
In 1 John he that commits (habitually practices) sin is set in opposition to the one who habitually practice righteous living. Consider the immediate context:
7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.
8 He that committeth (habitually practices) sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
9 Whosoever is born of God doeth not commit (habitually practice) sin; for his seed remaineth in him: and he cannot (habitually practice) sin, because he is born of God.
10 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 3:7-10
As you can see, it has nothing to do with any sort of concept that your soul or spirit cannot sin. It actually is referring to your conduct and actions.
With regards to sin not being able to affect a person’s soul, Paul tells the believers at Corinth “Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God.” ~ 2 Corinthians 7:1
Notice that Paul tells them to cleanse themselves from all filthiness of the flesh and spirit. The letters of first and second Corinthians were written to believers and not to a mix of believers and unbelievers. Notice that Paul includes himself in the statement above, using the pronoun us: “let us cleanses ourselves…”
In 1 Corinthians Paul had rebuked the Corinthian believers for allowing fornication of go on in their midst. In 2 Corinthians, after they repented and dealt this sin, Paul writes the following:
8 For though I made you sorry with a letter, I do not repent, though I did repent: for I perceive that the same epistle hath made you sorry, though it were but for a season.
9 Now I rejoice, not that ye were made sorry, but that ye sorrowed to repentance: for ye were made sorry after a godly manner, that ye might receive damage by us in nothing.
10 For godly sorrow worketh repentance to salvation not to be repented of: but the sorrow of the world worketh death.
11 For behold this selfsame thing, that ye sorrowed after a godly sort, what carefulness it wrought in you, yea, what clearing of yourselves, yea, what indignation, yea, what fear, yea, what vehement desire, yea, what zeal, yea, what revenge! In all things ye have approved yourselves to be clear in this matter. ~ 2 Corinthians 7:8-11
Notice that the repentance of the Corinthians had an effect on their spiritual disposition. Sin absolutely does have an effect on our soul, that is why we need cleansing with the precious blood of Jesus through the power of the Holy Spirit when we sin.
Consider also 1 Thessalonians 5:23:
And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ.
Notice that Paul’s prayer for the Thessalonians was that their whole spirit, soul and bodies would be preserved blameless until the coming of the Lord.
In the book of the Revelation, Jesus said the following to the church at Sardis:
2 Be watchful, and strengthen the things which remain, that are ready to die: for I have not found thy works perfect before God.
3 Remember therefore how thou hast received and heard, and hold fast, and repent. If therefore thou shall not watch, I will come on thee as a thief, and thou shall not know what hour I will come upon thee.
4 Thou hast a few names even in Sardis which have not defiled their garments; and they shall walk with me in white: for they are worthy.
5 He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels. ~ Revelation 3:2-5
Notice that some of these had defiled their spiritual garments and Jesus had not found their works perfect in the sight of God. Now, going back to 1 John notice the reference to works:
VERSE 8: He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the works of the devil.
VERSES 9-12 Whosoever is born of God doth not commit (habitually practice) sin; for his seed remaineth in him: and he cannot (habitually practice) sin, because he is born of God.
10 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.
11 For this is the message that ye heard from the beginning, that we should love one another.
12 Not as Cain, who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother’s righteous.
The works being referred to by John are our actions. John goes on to say the following:
13 Marvel not, my brethren, if the world hate you.
14 We know that we have passed from death unto life, because we love the brethren. He that loveth not his brother abideth in death.
15 Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him. ~ 1 john 3:10-15
Sin affects the whole man, not just outwardly.