2 “Judas also,” he says, “who betrayed Him, knew the place; for Jesus oft-times resorted there with His disciples.” There, accordingly, the wolf, clad in a sheep's skin, and tolerated among the sheep by the profound counsel of the Father of the family, learned where he might opportunely scatter the slender flock, and lay his coveted snares for the Shepherd. “Judas then,” he adds, “having received a cohort, and officers from the chief men and the Pharisees, comes there with lanterns, and torches, and weapons.”
It was a cohort, not of Jews, but of soldiers. We are therefore to understand it as having been received from the governor, as if for the purpose of securing the person of a criminal, and by preserving the forms of legal power, to deter any from venturing to resist his captors: although at the same time so great a band had been assembled, and came armed in such a way as either to terrify or even attack any one who should dare to make a stand in Christ's defense. For only in so far was His power concealed and prominence given to His weakness, that these very measures were deemed necessary by His enemies to be taken against Him, for whose hurt nothing would have sufficed but what was pleasing to Himself; in His own goodness making a good use of the wicked, and doing what was good in regard to the wicked, that He might transform the evil into the good, and distinguish between the good and the evil.
Source: Tractates on the Gospel of John (New Advent)