'Flesh' in the Bible

Now if I live on in the flesh, this means fruitful work for me; and I don’t know which one I should choose.

but to remain in the flesh is more necessary for you.

Watch out for “dogs,” watch out for evil workers, watch out for those who mutilate the flesh.

For we are the circumcision, the ones who serve by the Spirit of God, boast in Christ Jesus, and do not put confidence in the flesh—

although I once also had confidence in the flesh. If anyone else thinks he has grounds for confidence in the flesh, I have more: