Theophylact of Ohrid

"So, having punished Him," he says, that is, having disciplined Him with scourges, "I will release Him." And it was fitting for the Romans, to please the Jews, to release one prisoner for the feast. For when making a covenant with the Jews, they gave them the freedom to live according to their own customs and laws. And the Jews had a custom from their fathers of requesting condemned men from the governor; just as they also interceded for Jonathan before Saul (1 Sam. 14:45). …

Commentary on Luke ↗

Bede

As if he said, I will subject Him to all the scourgings and mockings you desire, but do not thirst after the innocent blood. It follows, For of necessity he must release one unto them, &c. an obligation not imposed by a decree of the imperial law, but binding by the annual custom of the nation, whom in such things he was glad to please.

Catena Aurea by Aquinas ↗

Bonaventure

And because it is unjust for such a one to be condemned, therefore he adds: I will therefore chastise him and release him, pronouncing an equitable sentence; for this sentence was to be delivered according to justice, since an innocent man was being accused. But Pilate did not dare to do this, but sought the assent of the adverse party, showing that he could not justly be condemned. …

Commentary on Luke, Chapter 23 ↗