Greet one another with a holy kiss. All the churches of Christ greet you.
Romans 16:16 ESV

A kiss on the cheek--often just touching cheeks together--was a common greeting in the Mediterranean cultures of the first century and remains so even today, although perhaps not quite as popular now as it was then.

It was also common, both then and now, to kiss sacred objects (idols, scrolls, amulets, etc.) as an expression of reverence. You can see this in the Catholic veneration of crucifixes and the Bible and the Jewish practice of touching a Torah scroll or Mezuzah and then kissing one's fingertips.

However, the idea of greeting one another “with a holy kiss” appears to be unique to Paul’s writings. I believe he intentionally combined the traditions of greeting and sacred veneration to emphasize how every disciple of Yeshua becomes a temple housing the Holy Spirit of God (1 Corinthians 3:16).