In an ethical sense opposed to "the spirit." Genesis 6:3, "for that lie also (even the race of godly Seth) (is become) flesh (carnal)." When the salt of the church has lost its savor, the whole mass is corrupt and ripe for judgment. 1 Corinthians 1:26, "wise after the flesh," i.e. with wisdom acquired by mere human study without the Spirit. Contrast Matthew 16:17; Matthew 26:41. Not the body, which is not in itself sinful; it was through thinking it so that Gnostic ascetics mortified it by austerities, while all the while their seeming neglecting of the body was pampering "the flesh" (Colossians 2:21-23). "The flesh" is the natural man, including the unrenewed will and mind, moving in the world of self and sense only.
Self imposed ordinances gratify the flesh (i.e. self) while seemingly mortifying it. "Trouble in the flesh" is in their outward state, namely, through the present distress (1 Corinthians 7:28). So John 6:63, "it is the Spirit that quickeneth; the flesh profiteth nothing; the words that I speak unto you, they are spirit and are life." Not the outward flesh, but the word of Christ, is what gives life. So Peter understood Christ, as his reply shows: "Thou hast the words of eternal life." "To know Christ after the flesh" (2 Corinthians 5:16) means to know Him in His mere outward worldly relations, with a view to "glorying" in them (John 8:15; Philemon 3:3-10); as Judaizing Christians prided themselves on the fleshly advantage of belonging to Israel, the nation of Christ, or on having seen Him in the flesh, as a ground of superiority over others (2 Corinthians 11:18; 2 Corinthians 10:7).
Contrasted with knowing Him spiritually as new creatures (2 Corinthians 5:12; 2 Corinthians 5:15; 2 Corinthians 5:17). Outward rebellions toward Him profit nothing (Luke 8:19-21; John 16:7; John 16:22; Matthew 7:22-23). All outward distinctions are lost sight of in experiment, ally knowing Him in His new resurrection life (Galatians 2:6; Galatians 2:20; Galatians 3:28; Romans 6:9-11; 1 Corinthians 15:45; 1 Peter 3:18; 1 Peter 4:1-2); disproving both Mariolatry and transubstantiation. In Romans 4:1, "what hath Abraham found, as pertaining to the flesh?" i.e. as respects carnal ordinances (circumcision). "All flesh," i.e. all men (Luke 3:2; John 17:2).