Albert Barnes Commentary Matthew 26:48

"Now he that betrayed him gave them a sign, saying, Whomsoever I shall kiss, that is he: take him." — Matthew 26:48 (ASV)

Gave them a sign. That is, told them of a way by which they might know whom to apprehend, namely, by his kissing him. It was night. Jesus was, moreover, probably personally unknown to the Romans, and perhaps to the others as well. Judas, therefore, being well acquainted with him, to prevent any possibility of mistake, agreed to identify him by one of the tokens of friendship.

John tells us that Jesus, knowing all things that would come upon him, when they approached him, asked them whom they sought. They replied, "Jesus of Nazareth." Jesus informed them that he was the person they sought. When they heard this, overawed by his presence and struck by the consciousness of guilt, they drew back and fell to the ground. He again asked them whom they sought. They made the same declaration: "Jesus of Nazareth." Jesus then, since they professed to seek only him, claimed the right that his disciples should be allowed to escape—that the saying might be fulfilled which he spake, Of them which thou gavest me have I lost none (John 18:9). See also John 17:12.