http://biblebitbybit.blogspot.com/2016/01/1-corinthians-16-v-20.html
Posted by 1 Corinthians on Saturday, 16 January 2016
1 Corinthians 16:20
All the brethren greet you. Greet ye one another with an holy kiss.
16:20. All the brothers may refer to those from the Corinthian church in Ephesus at the time of writing (1:11; 16:17), or to believers in Ephesus who met in a house(s) other than that of Aquila and Priscilla, or simply to the collective community of Christians in the province of Asia.
The holy kiss (cf. 2 Cor. 13:12; Rom. 16:16; 1 Thes. 5:25; 1 Peter 5:14) was primarily a symbolic expression of the love, forgiveness, and unity which should exist among Christians. As such, it became associated with the celebration of the Lord’s Supper as a prelude to its observance (cf. Justin Apology 1. 65. 2). It was a mark of the familial bond which united believers. There is no indication that it was restricted to one’s own sex in the New Testament era (cf. Luke 7:37, 45). The suggestion to separate the sexes for the exchange of the kiss arose in the late second century due to concern about criticism from non-Christians and the danger of erotic abuse (cf. Athenagorus Supplication 32; Clement of Alexandria Pedagogue 3. 81. 2-4). By the third century it seems that the sexes were separated (Apostolic Constitutions 2. 57. 17), and by the fourth century the clergy and laity were also kept apart (Apostolic Constitutions 8. 11. 9). Such, however, was apparently not the case in the New Testament church where love for one another was openly expressed.
Excerpt from:
Walvoord, J. F., Zuck, R. B., & Dallas Theological Seminary. (1983-c1985).
The Bible Knowledge Commentary : An Exposition of the Scriptures.
Wheaton, IL: Victor Books.