When we place our trust in Jesus Christ as omnipotent Creator and gracious Redeemer, He then faithfully undertakes to provide everything we need to live an effective, fruitful, victorious Christian life.
For example, when we are tempted to sin or are tested in any other way, "God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it" (1 Corinthians 10:13). In this connection, He undertakes to ground us firmly in His truth and to keep us from moral and spiritual harm. "The Lord is faithful, who shall stablish you, and keep you from evil" (2 Thessalonians 3:3).
When we do sin, however, He assures us that "if we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness" (1 John 1:9). With all our failings, He has undertaken to eventually perfect us in Christ, and He faithfully will continue this until it is done. "And the very God of peace sanctify you wholly; . . . Faithful is he that calleth you, who also will do it" (1 Thessalonians 5:23-24).
All that He has promised, He will do. Even when we are unfaithful to Him, He remains faithful to us. "If we believe not [that is, 'are unfaithful'], yet he abideth faithful: he cannot deny himself" (2 Timothy 2:13).
Today's verse above, assuring us of God's faithfulness, follows the promise that He will "confirm you unto the end, that ye may be blameless in the day of our Lord Jesus Christ" (1 Corinthians 1:8). Therefore, we seek also to be faithful. "Let us hold fast the profession of our faith without wavering; (for he is faithful that promised;)" (Hebrews 10:23). HMM