"For we are the circumcision, who worship God in the Spirit, rejoice in Christ Jesus, and have no confidence in the flesh..." – Philippians 3:3
Putting confidence in the flesh is a no-no for all Christians who have professed their faith in Christ. All who have followed Christ from salvation know that it is wrong to trust in the flesh. After all, the flesh is against God.
What the Flesh Is
Everyone knows that "flesh" is simply the material from which our bodies are primarily constructed. This kind of flesh is made by God, and in Christ it is made into a temple of the Holy Spirit. This flesh is the one the Psalmist meant in Psalm 84:2.
"My soul longs, yes, even faints for the courts of the Lord; My heart and my flesh cry out for the living God."
The Flesh that I am referring to, however, is a different kind of flesh. In the New Testament, references to the flesh often speak of the sinful nature, a character or quality that is against God. Consider what the apostle Paul said in Galatians 5:16-17.
"I say then: Walk in the Spirit, and you shall not fulfill the lust of the flesh. For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, so that you do not do the things that you wish."
My friends, it is easy to spot the difference between the two. The first is the physical flesh that we have, and our skills, talents and personal capabilities. The second is the sinful nature, character, and attitude that prefers to do what God doesn't like.
Why We Must Put No Confidence in the Flesh
The Bible clearly tells us that we must not put our confidence in the flesh. Some might say that it's the sinful nature we must never ever rely on, but the literal flesh we can. I beg to differ: we shouldn't trust both.
Putting our confidence in our literal flesh, or abilities and capacities, is good only for some things. Exercise builds our bodies up. But we can never do the things of the Spirit using our own skills. It's not by our might or power, but by the Spirit of God (see Zechariah 4:6).
Putting our confidence on our sinful nature, on the other, hand is foolishness. It assures us of failures, and guarantees that we could never ever live a life pleasing to God. What it does guarantee, however, is non-entry to the Kingdom of God.
"When you follow the desires of your sinful nature, the results are very clear... Let me tell you again, as I have before, that anyone living that sort of life will not inherit the Kingdom of God." (see Galatians 5:19-21)
"Therefore, dear brothers and sisters, you have no obligation to do what your sinful nature urges you to do. For if you live by its dictates, you will die. But if through the power of the Spirit you put to death the deeds of your sinful nature, you will live." (Romans 8:12-13)