Theophylact of Ohrid — as excerpted in the Catena Aurea on Luke 22:7-13

“He sends them for this reason to an unknown man: to shew them that He voluntarily underwent His Passion, since He who so swayed the mind of one unknown to Him, that He should receive them, was able to deal with the Jews just as He wished. But some say that He gave not the name of the man, lest the traitor knowing his name might open the house to the Pharisees, and they should have come and taken Him before that the supper was eaten, and He had delivered the spiritual mysteries to His disciples. But He directs them by particular signs to a certain house; whence it follows, And ye shall say to the goodman of the house, The Master saith, Where is the guestchamber, &c. And he will shew you an upper room, &c.”