John Chrysostom

Or, because whenever they had hitherto attempted to seize Him, He had escaped them they knew not how; as also He might then have done had He been so minded.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

Judas gave a sign because it was night and they were not able to identify Jesus. For those who came to arrest Him were not from the multitude, but were servants of the high priest, who perhaps did not know Jesus at all. But the disciple reveals the Master to them with a kiss.

Commentary on Matthew ↗

Jerome

But he who betrayed him gave them a sign, saying: Whomever I shall kiss, that is he, hold him fast. Miserable Judas, and yet not pitiable, with the same unfaithfulness with which he betrayed his master and Lord, he believed that the signs which he had seen the Savior performing were not done by divine majesty, but by magical skills. And because he had heard that he was transfigured on the mountain, he feared that he might slip away from the hands of the attendants through a similar transformation. …

Commentary on Matthew ↗

Hilary of Poitiers

There is a certain order to the different facets of Christ's suffering. But the reason for Judas's kiss was that we might discern all our enemies and those who we know would delight in raging against us. The Lord does not resist his kiss.

Commentary on Matthew 32.2 ↗

Thomas Aquinas

Next he treats of the sign of betrayal: and he that betrayed him gave them a sign, saying etc. But here there is a question. Since he was well known in Judea, why did they seek a sign? A twofold reason can be given. One is that Judas had heard that Christ was transfigured on the mountain, and he believed this had been done by magical art; therefore, he wanted to anticipate with the sign of a kiss, before he could transfigure himself. Jerome sets forth this explanation. …

Commentary on Matthew ↗