3 But the Lord is faithful, who will establish you and guard you from the evil one. NKJV
“But the Lord is faithful” The word “faithful” gives the meaning that the promises found in the Scripture, God will see it through until it is accomplished. No one can thwart God’s plan.
“who will establish you” refers to presenting the believer in Christ blameless and faithful until the end.
“guard you from the evil one” The Lord will protect all genuine believers from being destroyed, losing their faith in Jesus from Satan and his demonic forces of evil.