“He will show you
A large room,
For us there!”
καὶ αὐτὸς ὑμῖν δείξει ἀνάγαιον μέγα ἐστρωμένον ἕτοιμον· καὶ ἐκεῖ ἑτοιμάσατε ἡμῖν.
There is something similar to this in Luke, chapter 22:12, but nothing about the description of this upstairs room in Matthew. Mark said that Jesus told the 2 unnamed disciples that the owner of this house would show them a large upstairs room (καὶ αὐτὸς ὑμῖν δείξει ἀνάγαιον μέγα). This room would be completely furnished (ἐστρωμένον) and already prepared (ἕτοιμον) for a meal. That is where they were to make the final preparations (καὶ ἐκεῖ ἑτοιμάσατε ἡμῖν) for the Passover meal for Jesus and his apostles. Thus, it would make sense if these two disciples were Peter and John, as Luke indicated, since they were among the 12 apostles, who would be later attending this Passover.