2 Corinthians 5:16(KJV) “Wherefore henceforth know we no man after the flesh…”
Paul is saying “From this moment on…” That was a point of turnaround where even the Apostle himself realized that it is not enough to understand a man according to his or her flesh.
That is a great mistake that many people make. They employ an individual on the basis of his flesh. They marry according to the flesh. But when it comes to comprehensively understanding a person, Paul is trying to make us to realise the importance of penetrating into the core of a person and getting to the spirit that resides in the flesh.
The flesh in that verse represents everything in the physical. If your study ends on the physical aspect of an object, then you know nothing about that thing.
If everything that you claim to know about a person is their flesh, then you know completely nothing about that person.
There is something about that person that you have to know and by knowing that thing, then you can claim that you have fully understood him/her.
You have to get to the spirit of a thing for you to fully understand it.
Follow the link to watch the full teaching;