2Co 13:5 Examine yourselves as to whether you are in the faith. Test yourselves. Do you not know yourselves, that Jesus Christ is in you? unless indeed you are disqualified.
This verse is often misapplied and misused. What the apostle Paul is actually saying in effect here is:
"You Corinthians are doubting my apostleship. Do you want proof that Christ is really speaking in me as an apostle? I will give you one: YOU YOURSELVES are my proof that I am an apostle. Examine yourselves! You became Christians because of me. Test your own selves. Don't you recognize that Christ is in you as a result of my ministry?--unless indeed you are disqualified. If you became genuinely saved because of my ministry, how can you be doubting my apostleship?"
Start reading from verse 3 and then jump all the way to verse 5 to get the idea. Verse 4 is a parenthesis, a digression.
2Co 13:3 since you seek a proof of Christ speaking in me, who is not weak toward you, but mighty in you.
(4 For though He was crucified in weakness, yet He lives by the power of God. For we also are weak in Him, but we shall live with Him by the power of God toward you).
5 Examine yourselves as to whether you are in the faith. Test yourselves. Do you not know yourselves, that Jesus Christ is in you? --unless indeed you are disqualified.
The Corinthians were being misled by the teachings of false teachers in their midst. These false teachers were convincing the Corinthians that the apostle Paul was not a genuine apostle. That his message was false. Many of the Corinthians were led away from Paul because of this.
A) The apostle Paul had to defend his ministry in this epistle. As an example, just read chapters 11 and 12.
B) 2Co 3:1 Do we begin again to commend ourselves? Or do we need, as some others, epistles of commendation to you or letters of commendation from you?
2 You are our epistle written in our hearts, known and read by all men;
3 clearly you are an epistle of Christ, ministered by us, written not with ink but by the Spirit of the living God, not on tablets of stone but on tablets of flesh, that is, of the heart.
Paul does not need to have a certificate or letters of commendation for the Corinthians to accept him. The Corinthians themselves were his living letters of commendation certifying his ministry. They became Christ's because of Paul.
C) He has been defending his apostleship since the first letter:
1Co 9:1 Am I not an apostle? Am I not free? Have I not seen Jesus Christ our Lord? Are you not my work in the Lord?
2 If I am not an apostle to others, yet doubtless I am to you. For you are the seal of my apostleship in the Lord.
3 My defense to those who examine me is this:
ILLUSTRATION
One time a watchmaker woke up one morning hearing loud noises in the basement. He found out that his watches were having a protest rally against him. They were screaming and holding up placards that read: "You are not a watchmaker!!! You are false!!! Give us proof that you are indeed a watch maker!!!"
The watchmaker replied: "You seek proof that I am a watchmaker??!! Well, look at yourselves! Have I not made you?! Are you not genuine watches because of me?!"
The apostle Paul in 2 Corinthians 13:5 was not telling the Corinthians to step back for awhile, have a neutral view of themselves and then find out whether they were indeed Christians or not. (Hey, the apostle Paul was sure that they were Christians. By the inspiration of the Holy Spirit, he called them "Brethren" 8 times in this epistle). He was telling them to examine themselves, confident that they will find out that they were indeed Christians. Vindicating his ministry as a result.
2Co 13:3 since you seek a proof of Christ speaking in me, who is not weak toward you, but mighty in you.
2Co 13:5 Examine yourselves as to whether you are in the faith. Test yourselves. Do you not know yourselves, that Jesus Christ is in you? --unless indeed you are disqualified.
2Co 13:6 But I trust that YOU will know that WE are not disqualified.
Look at yourselves! I trust that you will find out that we are genuine indeed.
The misapplication and misuse of this verse has often resulted in morbid introspection, depression and doubts concerning one's salvation. A Christian can never find assurance of salvation by looking at self. King David would surely have severe doubts concerning his salvation looking at his life when he backslid from God for a year. A sinner is saved by trusting in the Word of God, he will be assured by the Word of God.
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His Blood makes us safe. His Word makes us sure. Holy and righteous living, loving the brethren, spiritual growth etc. are confirmatory evidences. But the source of assurance is the Word of God; His promise and guarantee that whoever genuinely trusts in His Son will be saved. The repentant thief on the cross had little time for spiritual growth, he had no opportunity to love the brethren. All he had was the sure word and promise of the Savior. And it was enough.
P.S. It is true that the Spirit bears witness with our spirit. But the Spirit witnesses through the Word, not apart from the Word.