1 Corinthians 16:20 - Ellicott's Commentary On The Whole Bible

An holy kiss. — The kiss was the ordinary form of affectionate greeting in the East. The Church adopted it; and when thus interchanged between those whose bond of friendship was not earthly, but spiritual, it was designated “the holy kiss.” (See Romans 16:16; 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.