It is better to trust in the LORD than to put confidence in man.
The importance of faith in our sanctification is hard to overstate, if for no other reason than the fact that not only is unbelief a great sin, but that the presence of faith is also one of the major determiners of whether something which is done is or isn’t sin. Paul states this clearly in Romans 14:23—”whatsoever is not of faith is sin”. Put in another way, we are sanctified by faith (Acts 26:18), and our sanctification will only go as far as our faith.
One storyline that keeps repeating in the Old Testament is the many sins that God’s people themselves committed when they failed to trust in God. The life of the Patriarch Abraham in the Book of Genesis is one entire story of God refining his faith. His unbelief in God’s protection was the reason he lied about Sarah twice and almost caused her to be adulterated had the Lord not mercifully intervened. More tragically, unbelief in God’s protection was also the reason God swore in his wrath that the first generation of Israelites in the Exodus from Egypt would not enter into the rest of the Promised Land (Heb. 3:19). Trusting in horses and chariots instead of the Almighty God to save them would be why the nation Israel later turned back to make political alliances with Egypt against what the Lord had already anticipated and commanded them not to do (Deut. 17:17; Is. 31:1). This resulted in the nation’s destruction and exile. It would be the same unbelief in the Lord Jesus Christ for which the Jews were eventually broken off from the olive tree of God’s covenant people (Rom. 11:20).
We must not think that we, New Testament saints, are immune from such unbelief. The author of the Book of Hebrews warns us rather severely, “Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God” (3:12). And how might we overcome such unbelief? The Apostle goes on and instructs us to exhort one another daily (v.13). We are to look unto Jesus, the author and finisher of our faith (12:2), who gives us the perfect example of walking by faith and not by sight when he trusted and obeyed the Lord even unto death.