Evil (poneros) = wicked; also contains the idea of being full of labor, toil, annoyances, hardships, and peril.
Paul is confident that God will help the Thessalonians do what is right (2 Thess. 3:3-4)
But... "enough about me -- now, about you!"
Faithful is the Lord = this is a direct contrast to the previous phrase "not all have faith." Even though not everyone believes the truth, the Lord is still to be believed in as being faithful to His promises!
He will strengthen = to set in a fixed position, establish, confirm one's mind (same verb as in 1 Th 3:13 and 2 Th 2:17).
Protect (phulasso) = to guard, watch over, keep safe. God will not establish or strengthen them and then leave them alone -- He will guard and protect them afterwards.
From the evil one = the context indicates that this refers to Satan (see 2 Th 2:9). The evil one always seeks to destroy "every good work and word."
Confidence in the Lord (peitho) = persuasion, assurance, a state of trust. This is the perfect tense: "We became persuaded concerning you and that persuasion is still with us now." Paul's confidence was not in the Thessalonians, but in the Lord -- in the faithfulness of God on their behalf.
You are doing and will do = the present and future tenses of poieo (to do or make). This word also means to act rightly or to do well.
What we command = to give an order or a commission to a task.
Paul [again] prays for them (2 Thess. 3:5)
May the Lord = the optative mood expresses a wish for the future (see 2 Th 2:16-17). Paul is praying for them again!
Direct your hearts = to make straight; to lay out a smooth and direct route.
Into the love (agape) of God = Paul prays that their hearts would be directed into the sphere or realm of the unselfish, sacrificial love that is characteristic of God Himself. This would provide increasing appreciation for God's own love for them, as well as the ability to express this kind of love to others (see 1 Th 1:3; 3:6, 12; 5:13; 2 Th 1:3).
Into the steadfastness (hupomone) of Christ = literally, "abiding under." This is the kind of patience that grows only under trial and affliction. The Thessalonians (and we) need this kind of steadfastness in order to endure affliction in a godly manner.
Points of Application:
We, too, should pray for those who minister to us. Christian leaders are men "subject to like passions as we are" (James 5:17), and they need our prayer support.
We need to be reminded that the Lord is faithful. He will strengthen and protect us.
We should ask ourselves, "Will God find me doing what I know to be right? Am I doing (present) and will I do (future) what He commands?" With God's help, I will.
We, too, should pray that God would provide a direct way for us to increase in agape love and to exhibit the kind of endurance in our circumstances that Christ demonstrated for us.