2 Thes. 3:1-5 (ESV)
Finally, brothers, pray for us, that the word of the Lord may speed ahead and be honored, as happened among you,  and that we may be delivered from wicked and evil men. For not all have faith.  But the Lord is faithful. He will establish you and guard you against the evil one.  And we have confidence in the Lord about you, that you are doing and will do the things that we command.  May the Lord direct your hearts to the love of God and to the steadfastness of Christ.
“But the Lord is faithful. He will establish you and guard you against the evil one.” It is quite reassuring that God is faithful, that the Lord is faithful. We like to think of ourselves as faithful, but the truth is we are often found wanting in this department. We try to be faithful. Christians strive to be faithful, and the fact that we are sinners is no excuse for being unfaithful. There is no excuse for sin. But there is forgiveness for it. It is in this forgiveness that the Lord establishes us and guards us against the evil one. Even when the evil one is successful in tempting us, God’s faithfulness prevails and forgives. So we rest in forgiveness. For “if we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.” His faithfulness is forgiveness.