13:1-6 Though it is God's gracious method to bear long with sinners, yet he will not bear always; at length he will come, and will not spare those who remain obstinate and impenitent. Christ at his crucifixion, appeared as only a weak and helpless man, but his resurrection and life showed his Divine power. So the apostles, how mean and contemptible soever they appeared to the world, yet, as instruments, they manifested the power of God. Let them prove their tempers, conduct, and experience, as gold is assayed or proved by the touchstone. If they could prove themselves not to be reprobates, not to be rejected of Christ, he trusted they would know that he was not a reprobate, not disowned by Christ. They ought to know if Christ Jesus was in them, by the influences, graces, and indwelling of his Spirit, by his kingdom set up in their hearts. Let us question our own souls; either we are true Christians, or we are deceivers. Unless Christ be in us by his Spirit, and power of his love, our faith is dead, and we are yet disapproved by our Judge.
5. Examine—Greek, "Try (make trial of) yourselves."
prove your own selves—This should be your first aim, rather than "seeking a proof of Christ speaking in me" (2Co 13:3).
your own selves—I need not speak much in proof of Christ being in me, your minister (2Co 13:3), for if ye try your own selves ye will see that Christ is also in you [Chrysostom], (Ro 8:10). Finding Christ dwelling in yourselves by faith, ye may well believe that He speaks in me, by whose ministry ye have received this faith [Estius]. To doubt it would be the sin of Israel, who, after so many miracles and experimental proofs of God's presence, still cried (Ex 17:7), "Is the Lord among us or not?" (Compare Mr 8:11).
except ye be reprobates—The Greek softens the expression, "somewhat reprobates," that is, not abiding the "proof" (alluding to the same word in the context); failing when tested. Image from metals (Jer 6:30; Da 5:27; Ro 1:28).