Commentaries:
This verse tells us that we can trust Him all the way to death because "He cannot deny Himself." God's very nature and character constitute a solemn obligation that He is His own law, that He is bound by what He is and that He can never be even in the smallest degree contradictory to or less than the level of His own consistent and uniform self. No wonder James 1:17 exclaims:
Every good gift and every perfect gift is from above, and comes down from the Father of lights, with whom there is no variation or shadow of turning.
As God, He must be true to the character of goodness and wisdom that His very name implies.
John W. Ritenbaugh
The Fruit of the Spirit: Faithfulness
A somewhat different use of the concept deny oneself occurs in II Timothy 2:13. God is faithful and cannot deny His character or His promises (Romans 3:3). However, a comparison of Paul's statement with Jesus' call to self-denial is enlightening. God, being so different from self-centered men, has nothing in His perfect character that needs to be denied. In His perfect goodness, God can only affirm Himself.
Martin G. Collins
Overcoming (Part 5): Self-Denial