“Now at the festival,
Pilate used to release
For whom they asked.”
Κατὰ δὲ ἑορτὴν ἀπέλυεν αὐτοῖς ἕνα δέσμιον ὃν παρῃτοῦντο.
This is almost word for word in Matthew, chapter 27:15. In John, chapter 18:39, there is something similar about the custom of releasing prisoners, but there is nothing in Luke about this custom. Mark said that at the festival time (Κατὰ δὲ ἑορτὴν), the Roman governor used to release one of the many prisoners to the Jewish people (ἀπέλυεν αὐτοῖς ἕνα δέσμιον), usually not a criminal facing the death penalty. This crowd could request the one that they wanted (παρῃτοῦντο), so that this kept the local folks happy. It is not clear how much this custom took place. Who would you ask for?