Matthew Henry on 2 Corinthians 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.