The Kiss is to salute with the lips, as a mark of affection, reverence, submission, forgiveness, etc. Christians kissed each other during prayer, Eucharist, baptism, and ordination and in connection with greeting, funerals, monastic vows, and martyrdom.
The Kiss of Judas
Judas was one of the twelve original apostles of Jesus and the treasurer of the disciples. Judas betrayed Jesus with a kiss and received thirty pieces of silver for it and then, guilt ridden, he hung himself. This deed of Judas is sometimes symbolised with coins and rope however, the church gave him no official symbol.
Luke 47: While He was still speaking, behold, a crowd came, and the one called Judas, one of the twelve, was preceding them; and he approached Jesus to kiss Him. 48 But Jesus said to him, “Judas, are you betraying the Son of Man with a kiss?”
Reference to the Kiss Christian Symbol in the Bible
The Easton Bible Dictionary provides the following definition, meaning and emblem for the Kiss Christian Symbol in the Bible. The Kiss was the sign of the following:
Of affection (Gen. 27:26, 27; 29:13; Luke 7:38, 45)
Of reconciliation (Gen. 33:4; 2 Sam. 14:33)
Of leave-taking (Gen. 31:28,55; Ruth 1:14; 2 Sam. 19:39)
Of homage (Ps. 2:12; 1 Sam. 10:1); spoken of as between parents and children (Gen. 27:26; 31:28, 55; 48:10; 50:1; Ex. 18:7; Ruth 1:9, 14)
Between male relatives (Gen. 29:13; 33:4; 45:15). It accompanied social worship as a symbol of brotherly love (Rom. 16:16; 1 Cor. 16:20; 2 Cor. 13:12; 1 Thess. 5:26; 1 Pet. 5:14).