Charles Ellicott Commentary 1 Corinthians 16:20

"All the brethren salute you. Salute one another with a holy kiss." — 1 Corinthians 16:20 (ASV)

A holy kiss.—The kiss was the ordinary form of affectionate greeting in the East. The Church adopted it; and when in this way interchanged between those whose bond of friendship was not earthly, but spiritual, it was designated “the holy kiss.” (1 Thessalonians 5:26.) The practice was given up in the Latin Church in the thirteenth century, but is still used in the Greek Church on certain great occasions, such as Easter Day.