See this explained in Matthew 26:48-56.
Betrayest thou the Son of man with a kiss? - By the “Son of man” was evidently meant “the Messiah.” Judas had had the most satisfactory evidence of that, and did not doubt it. A kiss was the sign of affection. By that slight artifice Judas thought to conceal his base purpose. Jesus with severity reproaches him for it. Every word is emphatic. “Betrayest” thou - dost thou violate all thy obligations of fidelity, and deliver thy Master up to death? Betrayest “thou” - thou, so long with him, so much favored, so sure that this is the Messiah? Betrayest thou “the Son of man” - the Messiah, the hope of the nations, the desire of all people, the world’s Redeemer? Betrayest thou the Son of man “with a kiss” - the sign of friendship and affection employed in a base and wicked purpose, intending to add deceit, disguise, and the prostitution of a mark of affection to the “crime of treason?” Every word of this must have gone to the very soul of Judas. Perhaps few reproofs of crime more resemble the awful searchings of the souls of the wicked in the day of judgment.