In most Mediterranean countries, Eastern, Western (e.g. Italy), or Middle-Eastern, it is common for people to “greet one another with a holy kiss” as the Apostle put it. Just as was the practice of the Jews in the temple, it was always the practice of the Orthodox to exchange such a kiss, as the Holy Apostles consistently exhort us: (Rom 16:16; 1 Cor. 13:12; 1 Cor. 16:20; 2 Cor 13:12; 1 Thess 5:26; 1 Pet 5:14). For the early Orthodox, this was a kiss on the lips (The venerable Handbook for Church Servers by Bulgakov describes this) but, since some people abused this piety, it became in most places a kiss on the cheeks. We know this as two kisses among some Orthodox communities, and three among others.
It has been customary for the Orthodox to offer words with the kiss, as it had been among the Patriarchs – the Jews, when saying the Shalom. Shortly, the kiss became reserved for persons of the same gender, and then eventually reserved as between the clergy in the liturgy, while it continued as a custom between all the people outside the liturgy. During the Kiss of Peace in the Divine Liturgy, the laity would generally exchange merely the words associated with the kiss (e.g. “Christ is in our Midst.” and “He is and ever shall be.”). This is still the most common practice, though some local Churches exchange actual kisses among the laity.
The glossary of Orthodox terminology on the Antiochian web site contains this entry for KISS OF PEACE: A kiss on the cheek or the shoulder given by one believer to another as a sign of Christian unity and fellowship (see 1 Cor. 16:20). The clergy, and in some places the faithful, exchange the kiss of peace before saying the Nicene Creed during the Divine Liturgy of the Orthodox Church.
One Orthodox writer (Frederica Mathewes-Green) describes the kiss in the context of venerating ikons:
We kiss stuff. When we first come into the church, we kiss the icons (Jesus on the feet and other saints on the hands, ideally). You’ll also notice that some kiss the chalice, some kiss the edge of the priest’s vestment as he passes by, the acolytes kiss his hand when they give him the censer, and we all line up to kiss the cross at the end of the service. When we talk about “venerating” something we usually mean crossing ourselves and kissing it.
Indeed, if we exchange the kiss with one another, it is meant as a form of mutual reverence, venerating each other as ikons of Christ, and presuming nothing of another’s worthiness. It can also, then, be a form of recognizing another person as greater than ourselves – of preferring others to ourselves. Likewise, it is a filial exchange, commending each to ourselves as family. The kiss is perhaps more a form of piety and humility for ourselves than for others, and yet becomes a sign of communal bond.
Finally, the Kiss is a symbol of reconciliation, similar in principle to two rivals shaking hands, albeit somewhat different in character. Our Lord instructed us to ‘leave our gift before the altar and go and be reconciled to our brother, should we remember that he has anything against us, and then come with the offering’; according to the penitential Psalm, only with such a ‘broken and contrite heart (with the proper attitude toward God and our brethren and our neighbor, if the Fathers are to be believed), can our sacrifices be acceptable’; only then, ‘shall we lay gifts on God’s altar’. Far from a mere gesture, nor merely as a token, a truly reverent and humble kiss, is as if to say, ‘If you have anything against me, which is quite likely in my unworthiness, then let us be reconciled.’ It is offered in our humility and piety.
Some reasons come to mind for kissing one another rather than simply using words or hugs: The words make a particular faculty of the mind active; far from being a merely sentimental feeling, we love one another with an active love – what is often distinguished as Charity. Likewise, the act of kissing is the physical form of bestowing – it represents bestowing love on another person as an active gift rather than only a feeling, and so indicates the moral responsibility of each bestower to maintain the activity of love, in a way perhaps akin to a spiritual discipline. It is a confession, then, also, of our doctrine of love – of what it is to us, versus the understanding offered to us by culture.
This is, in fact, seen in all the kisses of veneration of all of the various types of ikons – the love is active and requires a total level of moral activity, one which is subject to change and must be maintained in the total context of Orthodox piety – dread of Judgement, victory over the passions, and spiritual sight and worship, as much as mutual affection. It is a recognition in fact that we love and venerate each other as we would the ikons, since that is what every Orthodox person is. It is a recognition that, in our weakness, love must be the fruit of the Spirit alive in us rather than merely emotions or sentiment.