Thomas Aquinas

2457 Why does the Evangelist add, but when they came to Jesus and saw that he was already dead, they did not break his legs? Surely Jesus was crucified between the two others? We should say that one soldier went to one of the criminals and another soldier went to the other one to break their legs, and when they were done with this they both came to Jesus. We are told why they pierced his side, because when the soldiers saw that he was already dead, they did not break his legs.

Commentary on John ↗

Bonaventure

But when they had come to Jesus. Here is noted the opening of Christ's side. And first he says why they did not break his legs, namely because he was dead: and this is what he says: When they saw that he was already dead, they did not break his legs: because they did this in order to hasten death.

Commentary on John, Chapter 19 ↗