“Greet one another with a holy kiss”
Greet one another with a holy kiss. All the churches of Christ send you greetings. (Romans 16:16 BSB)
What it sounds like today
A quaint liturgical instruction.
The cultural key
The kiss was the greeting of kin: family members, close friends, honored teachers (which is what made Judas' kiss legible as betrayal). Commanding it across a whole congregation made the church greet as one family, and that family included slave and free, Jew and Gentile, patron and client, people who in any other Roman room would never exchange a kiss as equals. Paul orders it in four letters, Peter once ('the kiss of love'); later apologists had to defend the practice against outsiders' gossip precisely because it was so socially strange.
Recovered meaning
A one-line liturgy of social demolition: the greeting reserved for blood relatives, exchanged across every line Rome drew. The kiss said what the theology argued: you are now kin.