I give thanks to my God always for you because of the grace of God that was given you in Christ Jesus, 5 that in every way you were enriched in him in all speech and all knowledge— 6 even as the testimony about Christ was confirmed among you— 7 so that you are not lacking in any gift, as you wait for the revealing of our Lord Jesus Christ, 8 who will sustain you to the end, guiltless in the day of our Lord Jesus Christ. 9 God is faithful, by whom you were called into the Fellowship of his Son, Jesus Christ our Lord.
1. Paul starts his letter as he often does with thanksgiving to God for the work done in the believers he's writing to. He gives thanks because grace was given to the believers and the believers are growing in the knowledge of God. They are maturing and becoming more like Christ everyday. Grace–the unmerited favor of God, was given to the believers in Christ that they escape from the punishment of their sins, yet not only in that way, but grace also to be enriched in Christ.
2. The believers are supplied with the charismata of the Spirit as they await the blessed hope (Titus 2:13). It is God’s grace which gives them the gifts of the Spirit and thereby sustains them to the end.
3. It is the Lord Jesus, say verses 7b-8, who will sustain the believers guiltless. First, let us start with what that does not mean. It obviously does not mean that we will never sin, for if we claim that we deny the truth (1John 1:8). But rather it means that we will be found guiltless before God, because the penalty of our sin was paid for. We have, through justification by faith, received the perfect righteousness of Christ, so when God looks upon us, He does not see our sin, but Christ's perfect and sinless righteousness. The word sustain in the Greek is βεβαιόω (bebaioo, G950) which means “to make firm, establish, confirm, make sure”  and “to confirm, establish; to render constant and unwavering, 1 Cor. 1:8; to strengthen or establish by arguments or proofs, ratify, Mk. 16:20; to verify, as promises, Rom. 15:8”. It is the Lord Jesus who will indeed render us constant and unwavering in our faith and righteousness by faith. The Lord Jesus is able to sustain us to the end in the condition which we are now in, namely, in faith and grace, having the gifts of the Spirit and waiting for the blessed hope.
4. The end is defined to be “the day of our Lord Jesus Christ.” This is the last day, the day of judgment when God will judge the world in righteousness and manifest who is guilty and who is guiltless. The Lord Jesus is therefore able not only to sustain us to the end, but to sustain is blameless and without guilt before the Father. He has the ability and willingness for all who are His. We do not have to fear that day because we will be found blameless, and we know from other Scriptures that our righteousness was not originated with us, but was actually given to us by grace through faith. The word ἀνέγκλητος (anegkletos, G410) means “that cannot be called into to account, unreproveable, unaccused, blameless” and denotes the fact that God will not be able to find a cause of damnation in us, because of Christ's perfect work. This is the condition that God is able to keep the believer in. How does this fit with “falling away” and actually not being sustained to the end blameless?
5. In this passage, we hear John 6:39-40. The same concept of the Son being responsible to keep the elect is present here. He is give...