1 John 5:9

If we receive the witness of men - As we are accustomed to do, and as we must do in courts of justice, and in the ordinary daily transactions of life. We are constantly acting on the belief that what others say is true; that what the members of our families, and our neighbors say, is true; that what is reported by travelers is true; that what we read in books, and what is sworn to in courts of justice, is true. We could not get along a single day if we did not act on this belief; nor are we accustomed to call it in question, unless we have reason to suspect that it is false. The mind is so made that it must credit the testimony borne by others; and if this should cease even for a single day, the affairs of the world would come to a pause.

The witness of God is greater - Is more worthy of belief; as God is more true, and wise, and good than people. People may be deceived, and may undesignedly bear witness to that which is not true - God never can be; men may, for sinister and base purposes, intend to deceive - God never can; people may act from partial observation, from rumors unworthy of credence - God never can; people may desire to excite admiration by the marvelous - God never can; people have deceived - God never has; and though, from these causes, there are many instances where we are not certain that the testimony borne by people is true, yet we are always certain that that which is borne by God is not false. The only question on which the mind ever hesitates is, whether we actually have his testimony, or certainly know what he bears witness to; when that is ascertained, the human mind is so made that it cannot believe that God would deliberately deceive a world. See the notes at Hebrews 6:18. Compare Titus 1:2.

For this is the witness of God ... - The testimony above referred to - that borne by the Spirit, and the water, and the blood. Who that saw his baptism, and heard the voice from heaven, Matthew 3:16, could doubt that he was the Son of God? Who that saw his death on the cross, and that witnessed the amazing scenes which occurred there, could fail to join with the Roman centurion in saying that this was the Son of God? Who that has felt the influences of the Eternal Spirit on his heart, ever doubted that Jesus was the Son of God? Compare the notes at 1 Corinthians 12:3. Any one of these is sufficient to convince the soul of this; all combined bear on the same point, and confirm it from age to age.