What does Paul mean by 'we do not know Christ after the flesh'?
Paul means that since Christ's death, burial, and resurrection and the revelation of the gospel of grace, believers no longer know or follow Christ according to His earthly, Law-era ministry to Israel. We do not go by the things He taught Israel while under the Law, because that program has ended.
Les explains that while Jesus' words are the Word of God and can have application, for the most part everything He said was to people living under the Law. For example, when lepers were cleansed, He told them to show themselves to the priests, but there is no temple worship today and believers are not under the Law. God even had the temple destroyed so there would be no temptation to hang on to temple worship. Paul therefore says that since the death, burial, and resurrection and the revelation of the gospel of grace, henceforth we do not know Christ after the flesh. We are no longer going by the things He taught to Israel under the Law.
Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.
More Questions
Why does Paul say in 2 Corinthians 5:16 that we know Christ no more after the flesh?
Paul can write that we know Christ no more after the flesh because God is separating Judaism and Christianity, so we no longer know Him according to the flesh.
Why does Paul say he no longer knows Christ after the flesh?
Because of his revelations on the road to Damascus and in Arabia, Paul no longer refers to Christ in his earthly ministry, which is what he means by knowing no man after the flesh.