John the Apostle
1 John 5:12BSB·traditional attribution

Whoever has the Son has life; whoever does not have the Son of God does not have life.

John Calvin Reformed @genevareformer

12 He that hath not the Son This is a confirmation of the last sentence. It ought, indeed, to have been sufficient, that God made life to be in none but in Christ, that it might be sought in him; but lest any one should turn away to another, he excludes all from the hope of life who seek it not in Christ.

Matthew Henry Presbyterian @wholebiblehenry

In those words we may observe, I. The privilege and stability of the real Christian: He that believeth on the Son of God, hath been prevailed with unfeignedly to cleave to him for salvation, hath the witness in himself, Jo1 5:10. He hath not only the outward evidence that others have, but he hath in his own heart a testimony for Jesus Christ.

Commenting on 1 John 5:10-13

John Gill Reformed Baptist @doctorgill

He that hath the Son,.... Has a spiritual and experimental knowledge of him, true faith in him; who has him dwelling in his heart, and living in him: hath life: not only spiritual life, being quickened by him, and living by faith on him, but eternal life; the knowledge he has of him is eternal life; he has it in faith and hope, and has...