1 John 5:20

“And we know that the Son of God is come, &c.] That the second Person in the Godhead, who is equal to the Father, and of the same nature with him, is come from the Father, from heaven into this world, not by local motion, but by assumption of nature; that he is come in the flesh, or is become incarnate, in order to work out salvation for his people, by his obedience, sufferings, and death; and this John and others knew, for they had personal knowledge of him, and converse with him; they saw him with their eyes, heard him, and handled him: he dwelt among them, preached to them, wrought miracles before them, which proved him to be what he was; and it may be known that the Messiah must become,…”

“Summary of our Christian privileges. is come--is present, having come. "HE IS HERE--all is full of Him--His incarnation, work, and abiding presence, is to us a living fact" [ALFORD]. given us an understanding--Christ's, office is to give the inner spiritual understanding to discern the things of God. that we may know--Some oldest manuscripts read, "(so) that we know." him that is true--God, as opposed to every kind of idol or false god (Jo1 5:21). Jesus, by virtue of His oneness with God, is also "He that is true" (Rev 3:7). even--"we are in the true" God, by virtue of being "in His Son Jesus Christ." This is the true God--"This Jesus Christ (the last-named Person) is the true God"…”

“And we know that the Son of God is come - We know this by the evidence that John had referred to in this Epistle, 1 John 1:1-4; 1 John 5:6-8. And hath given us an understanding - Not an “understanding” considered as a faculty of the mind, for religion gives us no new faculties; but he has so instructed us that we do understand the great truths referred to. Compare the notes at Luke 24:45. All the correct knowledge which we have of God and his government, is to be traced directly or indirectly to the great Prophet whom God has sent into the world, John 1:4, John 1:18; John 8:12; John 9:5; Hebrews 1:1-3; Matthew 11:27. That we may know him that is true - That is, the true God. See the notes at…”

“And we know - By all these infallible proofs. That the Son of God is come - Into the world. And he hath given us a spiritual understanding, that we may know him, the true one - "The faithful and true witness." And we are in the true one - As branches in the vine, even in Jesus Christ, the eternal Son of God. This Jesus is the only living and true God, together with the father and the Spirit, and the original fountain of eternal life. So the beginning and the end of the epistle agree. 1 John 5:21”

“5:20 The NLT interprets the phrase the true God as referring to God, since the next phrase refers to his Son, Jesus Christ. John is also saying that Jesus Christ is the only true God (see John 1:1, 18; 20:28; Rom 9:5; Titus 2:13; 2 Pet 1:1). • To have fellowship with Jesus Christ is to have eternal life, because he is eternal life (1 Jn 5:12; see John 1:4; 3:16; 14:6; 20:31).”

“we know: Jo1 5:1, Jo1 4:2, Jo1 4:14 and hath: Mat 13:11; Luk 21:15, Luk 24:45; Joh 17:3, Joh 17:14, Joh 17:25; Co1 1:30; Co2 4:6; Eph 1:17-19, Eph 3:18; Col 2:2, Col 2:3 him that: Joh 14:6, Joh 17:3; Rev 3:7, Rev 3:14, Rev 6:10, Rev 15:3, Rev 19:11 and we: Jo1 2:6, Jo1 2:24, Jo1 4:16; Joh 10:30, Joh 14:20, Joh 14:23, Joh 15:4, Joh 17:20-23; Co2 5:17; Phi 3:9 This is: Jo1 5:11-13, Jo1 1:1-3; Isa 9:6, Isa 44:6, Isa 45:14, Isa 45:15, Isa 45:21-25, Isa 54:5; Jer 10:10, Jer 23:6; Joh 1:1-3, Joh 14:9, Joh 20:28; Act 20:28; Rom 9:5; Ti1 3:16; Tit 2:13; Heb 1:8 1 John 5:21”