Verse 1
advocate
Advocacy is that work of Jesus Christ for sinning saints which He carries on with the Father whereby, because of the eternal efficacy of His own sacrifice, He restores them to fellowship. CF Psalms 23:3. (See Scofield "John 13:10").
sin Sin. (See Scofield "Romans 3:23").
Verse 2
propitiation (Greek - ἱλασμός, that which propitiates). (See Scofield "Romans 3:25").
the sins Omit words "the sins.".
world kosmos = mankind. (See Scofield "Matthew 4:8").
Verses 3–4
commandments
John uses "commandments":
(1) in the general sense of the divine will, however revealed, "his word" (1Jn 2:5); and (2) especially of the law of Christ Galatians 6:2; 2 John 1:5. See, also, John 15:10-12.
Verses 5–11
perfect
(See Scofield "Matthew 5:48").
Verse 12
sins
Sin. (See Scofield "Romans 3:23").
Verses 13–14
little children
The little ones of the family; (See Scofield "1 John 2:28").
Verses 15–18
world
kosmos = world-system. 1 John 3:13; John 7:7. (See Scofield "Revelation 13:8").
Verses 19–27
went out from us
"Went out from us," that is, doctrinally. Doubtless then, as now, the deniers of the Son 1 John 2:22,23 still called themselves Christians. Cf 2 Timothy 1:15.
Verses 28–29
little children
The general term for all children.