I believe when Jesus said that there would come a time when there would be those He'd say He never knew ...the best I can figure, it must be those void of knowing Him.  We are to accept Jesus, but also what He expects out of us.   Some of us don't have a very high perception of what that is ...but I'd say it definitely includes what He says.  That certainly doesn't mean we have to be perfect ...but we should always represent Him as being perfect, and always take exactly what He says with high value, which is how we glorify Him.