See Poole on "Romans 16:16". See Poole on "1 Corinthians 16:20". It was an ancient custom and of common use, when friends met, for them (as a token of mutual love and friendship) to kiss each other: the Christians used it also at their ecclesiastical assemblings. It must not be looked upon as a precept, obliging all Christians to do the like; but only as directing those that then did use it, to use it innocently, chastely, sincerely, and holily.
Related Commentaries of 2 Corinthians 13:12
2 Corinthians 13:12
12 Greet one another with an holy kiss.