The Apostle did not mean that we should pay no attention to the shortcomings of the flesh, either in ourselves or in other disciples of Christ. All fleshly weaknesses should be striven against, and they may frequently demand rigorous treatment in the interest of the new heart, mind and will; but nevertheless, we are to differentiate distinctly between it and the weak mortal body, and are to love and sympathize with the brother or sister, while it may be necessary for us, in his or her interest, and also in the interest of the Church, to reprove or rebuke or otherwise correct the wrong course. The Apostle's definition as to how we are to know the two classes apart is that the unregenerate will mind the things of the flesh, while the regenerate will mind the things of the Spirit.
To know others after the flesh is to think of and to appreciate them from the standpoint of human nature. He knows others after the flesh who esteems and treats them according to something in their humanity, such as beauty, sex, wealth, strength, position, reputation, affiliation, etc. If we find ourselves more favorable toward some of the brethren for these and similar advantages than we would be if they lacked them, we know them according to the flesh. Our esteem of others should be based upon their relation to the Lord and His Truth. The more Christlikeness we see in them, the more we should esteem them; the less Christlikeness we see in them, the less we should esteem them, thus knowing them according to the Spirit.
Deut. 33:9; 1 Sam. 2:29; 1 Tim. 5:21; 2 Cor. 11:22; Gal. 2:11-14; Matt. 10:37; 12:48-50; John 2:4; 6:63; 15:14; Gal. 2:5, 6; 5:6.
