The Ignatius Catholic Study Bible New Testament (281 page)

1:1 the beginning:
I.e., when the Christian message first reached the original readers (2:7, 24; 3:11). There is also an allusion to "the beginning" mentioned in Jn 1:1, where the reference points back to the dawn of creation, when God brought all things into being through his divine Son (1 Jn 2:1314; 3:8).
the word of life:
The good news of the gospel. Its focus is the personal "Word" of the Father, Jesus Christ (Jn 1:1; Rev 19:13). See word study:
Word
at Jn 1:1. 
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1:2 with the Father:
Christ embodies the eternal life (5:11) that he shares with the Father in his divinity (Jn 5:26). This means that Christ himself is "true God" (1 Jn 5:20; Jn 1:1) and that he reveals to us the mystery of God's inner life as a Trinity (Jn 1:18). 
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1:3 fellowship:
The interpersonal communion that believers have with God and with one another (1:6-7). It is based on a common participation in divine life that establishes us as God's children (3:1). The apostles extend this gift to others by their preaching and sacramental ministry (1 Cor 10:16-17; CCC 425). 
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1:5 God is light:
Means that God is infinite goodness, purity, and truth.
darkness:
Stands for all things evil and erroneous that are churned out by the devil (Jn 3:19-21). Fellowship with God is impossible unless believers live in the light—loving as God loves and staying pure from sin as God is pure (1 Jn 1:6-7). This black-and-white vision of the world is also shared by the Jewish authors of the Dead Sea Scrolls, who made similar contrasts between spiritual realities in terms of light and darkness. 
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1:8 we have no sin:
An outrageous claim. John cautions readers that stubborn refusal to admit sin is a delusion and at the same time an insult to God (1:10) (CCC 827). 
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1:9 If we confess:
John envisions, not a general admission of weakness or even sinfulness, but the confession of specific acts of wrongdoing (Ps 32:3-5). God, for his part, is eager to show mercy to the contrite spirit (Ps 51:17). Contrary to the teaching of some, the need for repentance, confession, and forgiveness is ongoing throughout the Christian life; otherwise, the Lord would not urge believers to seek forgiveness on a continuing basis (Mt 6:12; Lk 11:4). Note that in biblical terms "confession" (Gk.
homologeō
) is something you do with your
lips
and not simply in the silence of your heart (Mk 1:5; Rom 10:10; Jas 5:16) (CCC 2631). • The Church encourages the private confession of sins to God. Ordinarily, however, this should lead us to the Sacrament of Reconciliation. Jesus implies as much in Jn 20:23, where he gives the apostles his own authority to remit or retain sins according to their discretion. This discretion could not be exercised apart from knowledge of specific sins acquired by the verbal confession of sinners (CCC 1461, 2839). • Priestly confession is not a Christian innovation but an extension and sacramental elevation of a practice long observed in Israel (Lev 5:5-6; Num 5:510). 
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2:1-6
John recognizes that sin can be a nagging problem in the lives of believers. It is not a problem without a solution, however, since Jesus Christ is our advocate (2:1), our sin-offering (2:2), and our moral example (2:6). 
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2:1 advocate:
Refers to an "attorney" or "defense lawyer" in contemporary Greek literature. Jesus spoke of himself (Jn 14:16) and of the Spirit in this way (Jn 14:26; 15:26). Advocacy is needed before the Father when our sins prompt the devil to bring accusations against us (Rev 12:10) (CCC 519). See word study:
Counselor
at Jn 14:16. 
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2:2 sins of the whole world:
The redeeming work of Christ embraces all times, all places, and all peoples (Jn 1:29). Not a single individual has lived or will live for whom Christ did not die (2 Cor 5:15; CCC 605).
See note on 1 Tim 2:4
. • One makes satisfaction for an offense when he offers the person offended something of equal or greater value. Christ, by suffering in a spirit of love and obedience, offered to God more than the recompense required for all the offenses of the human race. His Passion was not only sufficient but superabundant satisfaction for the world's sins (St. Thomas Aquinas,
Summa Theologiae,
III, 48, 2). 
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2:3 keep his commandments:
The Father gives guidance to his children (3:1) for living and growing in maturity. Obedience to his commandments gives us the moral certitude that we are living as true sons and daughters. In essence, this amounts to imitating Christ (2:6), who showed us how to follow the Father's commandments without exception or fault (Jn 15:10). 
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2:6 the same way
 . . .
he walked:
Assumes readers are familiar with the life and ministry of Jesus, probably from the Gospel of John (CCC 2470). 
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2:7 no new commandment:
John's teaching is not a recent innovation unfamiliar to his readers. It is, rather, the commandment to love one another (2:10) that they received with the gospel and that ultimately goes back to Jesus (Jn 13:34). The point is that John's catechesis is an authentic expression of apostolic doctrine (CCC 2822).
See note on Jn 13:34
. 
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2:8 the true light:
Refers to the gospel in general and to Jesus Christ in particular (Jn 1:9). 
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2:9 He who says
 . . .
and hates:
A believer's conduct must agree with his confession for his fellowship with God to be genuine. Faith without faithfulness is not a saving faith at all (Jas 2:14-17).
See note on Jn 3:36
. 
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2:12-14
Readers are assured that Christ's blessings have come upon them: their sins are
forgiven
(2:12), they
know
the living God (2:13-14), and they are victorious over the
Evil One
(2:13-14). It is possible that John's address to children, fathers, and young men refers, not to various age groups, but to three levels of spiritual maturity (1 Cor 3:1; Heb 5:12-14). 
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2:15-17
John urges readers to let go of the world and embrace the Father (4:4). Although God made (Gen 1:1) and loves the world (Jn 3:16), the human family turned against him and surrendered itself to the devil (1 Jn 5:19). Since then, the propensity of fallen man is to love the world in selfish and disordered ways—feeding his
flesh
with its pleasures, his
eyes
with its possessions, and his spirit with its
pride.
Christians are called to renounce the world, not as something evil or detestable, but as something that threatens to consume our attention and turn our affections away from God. The ascetical disciplines of prayer, fasting, and almsgiving are venerated in Jewish and Christian tradition as practical ways to express our love for God and lessen our love for the world (Tob 12:8-10; Mt 6:2-18) (CCC 377, 2514). For different meanings of the term "world" in the writings of John,
see note on Jn 1:10
. 
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2:18 the last hour:
The final phase of salvation history set in motion by Christ. Paul refers to this last epoch as "the end of the ages" (1 Cor 10:11), just as Peter calls it "the end of the times" (1 Pet 1:20). These and similar expressions underscore the need for Christians to remain vigilant as they wait in joyful hope for the Lord's return in glory (CCC 670).
antichrist:
Or, "anti-messiah". Here the title applies to anyone who denies that Jesus is the anointed "Christ" or "Messiah" of Jewish expectation (1 Jn 2:22; 4:3; 2 Jn 7). In a restricted sense, the "Antichrist" is a blasphemous figure expected to appear at the end of days. His coming will thrust the Church into a time of persecution and set off an explosion of evil and deception in the world at large (CCC 675-77). For a description of this eschatological villain, see 2 Thess 2:3-11. 
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Word Study

Expiation
(
1 Jn 2:2
)

Hilasmos
(Gk.): a term that can mean "propitiation" with reference to God or "expiation" with reference to sin. The word is used only twice in the NT (1 Jn 2:2; 4:10) but is related to other biblical terms with a similar meaning (Lk 18:13; Rom 3:25; Heb 2:17). In all of these instances, the notion of removing or wiping away sin is in view. The basis for this understanding comes from the Greek OT, where
hilasmos
is a cultic term that refers to an expiatory sacrifice of atonement (Num 5:8; Ezek 44:27; 2 Mac 3:33). John interprets the death of Jesus along the same lines: the shedding of his blood on the Cross was an act of sacrifice that takes away the sins of the world (Jn 1:29; 1 Jn 1:7) (CCC 457, 614).

2:19 They went out:
I.e., the heretical secessionists, who broke away from the Church in order to follow their corrupt ways. For John, their departure is a sure sign of their deviation from the apostolic faith. The comment at 2:26 suggests the apostates were not content simply to leave, but were making active attempts to carry others astray with them. 
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2:20 anointed:
Refers to a special grace of the Holy Spirit, which instructs believers in the truth and alerts them to false teaching (2:26-27). There is a close relationship between confessing Jesus as the Messiah (Gk.
Christos,
2:22) and receiving his anointing (Gk
chrisma,
2:27), for the same Spirit who anointed Jesus (Acts 10:38) dwells in the hearts of all who are baptized in his name (Acts 2:38) (CCC 695). • Isaiah foresaw the anointing of the Messiah, not with oil, like the prophets, priests, and kings of Israel, but with the Spirit of Yahweh (Is 61:1). The descending Spirit brings many gifts with him, including wisdom, understanding, and knowledge (Is 11:2). • Vatican II teaches that all the faithful, clergy and laity alike, are anointed with a supernatural insight into the gospel (known in Latin as the
sensus fidei
). Graced in this way, the Church as a whole, guided by the teaching authority of the pope and bishops, will always give universal consent to the truth about Christian faith and life (
Lumen Gentium
12) (CCC 91-93).
the Holy One:
Probably refers to Jesus (Mk 1:24; Jn 6:69), though the Father bears this title, as well (Job 6:10; Is 1:4). 
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