New Defender's Study Bible Notes
1:6 will perform it. It is neither our responsibility nor within our capability to maintain ourselves in a state of salvation. God began this work in us (Ephesians 2:8), and He will assure its continuance.
1:6 day of Jesus Christ. The “day of Jesus Christ” (I Corinthians 1:8; 5:5; II Corinthians 1:14; Philippians 1:10; 2:16; II Thessalonians 2:2) is the day when Christ returns for His people (John 14:2-3).
1:7 defence. “Defence” is the Greek apologia, a legal term referring to a formal defense as in a courtroom. Many modern evangelicals think the gospel does not need to be defended—just preached. Paul and Timothy knew better. The gospel was under attack in their day, and is even more so now, and it does need a sound defense. See also Philippians 1:17.