Greet one another with a holy kiss. All the churches of Christ greet you.Romans 16:16 RSV
The salutation here is not that of Paul, as if he had said, “Kiss everyone for me,” but the salutation of the members themselves for one another with a sacred kiss of Christian love.
Such a kiss, upon the brow, or cheek, sometimes on both cheeks, or upon the hands, as in the Greek orthodox church until this day, was a common form of salutation in ancient times.
It was brought over into Christianity by apostolic commandment and continued for many centuries, prevailing as custom in many places yet.
All the churches of Christ … refers to Christians wherever in that period of time, and especially to the congregations founded by the apostle Paul.