1 Corinthians 16:20
All the brethren greet you. Greet ye one another with an holy kiss.
Note 8 at 1Co 16:20: It was a Middle Eastern custom to greet others with a kiss, as it still is today. However, Paul was not just restating a custom that was already practiced. That would be unnecessary. He was at the least saying that Christians should express their brotherly love toward each other. Many people in Western cultures would be offended by a kiss. Discretion should be used. It has to be a holy kiss, implying that there is an unholy kiss. If it offends the person receiving it, it's not proper.