2 Corinthians 5:16

Wherefore henceforth know we no man after the flesh i.e. we regard no man from a purely fleshly point of view (see note on ch. 2 Corinthians 1:17), but look upon him as endowed with a new vital principle from above which has changed his heart. Cf. 2 Corinthians 5:17; Rom 8:1-11; 1 Corinthians 2:10-16. "Even in Christ a transition took place analogous to that which happened to man in regeneration. In the Resurrection the life according to the flesh passed over into a life according to the Spirit." Olshausen. "He who knows no man after the flesh has entirely lost sight in the case of a Jew, for example, of his Jewish origin, in the case of a rich man of his riches, in that of a learned man of his learning, in that of a slave of his slavery, and so on." Meyer. Cf. Matthew 3:9; John 8:39; Romans 2:28-29; Rom 10:12; 1 Corinthians 12:13; Galatians 3:28; Colossians 3:11.

yea, though we have known Christ after the flesh i.e. from a purely human point of view, as the Son of David simply (Romans 1:3), not as the Incarnate Son of God, the Divine Word. See Bishop Wordsworth's note here. St Paul, and many others of the first preachers of the faith (cf. Acts 1:6), had started with such carnal conceptions, but they had disappeared before the light of God's truth.