Theophylact of Ohrid

"And having led him out of the city, they began to stone him." Finding themselves utterly unable to put an end to Stephen's speech, they "began to stone him." Even if he had been speaking falsely, he should have been released as a madman. But if he was speaking the truth, they should rather have marveled. "And having led him out of the city," they kill him, just as they also did with Jesus. …

Commentary on Acts ↗

Oecumenius

A witness says, whom they induced to bear false witness against him. And he points out the men who seemed to be witnesses, that they were more prepared for murder, for even their garments they laid aside to be nimble and light for casting stones. And he says that the one who would later be a messenger of the inhabited world also then took part in the murder, showing that some divine and wondrous and not merely human was the later change in him. …

Commentary on Acts ↗

Gregory the Dialogist

Often one who is seen to come after us surpasses us through the swiftness of good work, and tomorrow we scarcely follow him whom today we seemed to precede. Certainly when Stephen was dying for the faith, Saul was guarding the garments of those who were stoning him. Therefore he himself stoned with the hands of all who were stoning, since he rendered them all free to stone, and yet in the holy Church he surpassed in labors that very one whom by persecuting he made a martyr.

Forty Gospel Homilies, Homily 19 ↗

Bede

And they cast him out of the city and stoned him. And the Lord suffered outside the gate, who chose us from the world into His heavenly kingdom and glory, and Stephen, as if a stranger to the world, is stoned outside the city. For he did not have a lasting city here, but sought the one to come with his whole mind. And by just change of things, the martyr directs his gaze from the world's heart to the heavens, the persecutor of hard neck sends his hands to the stones. …

Commentary on Acts ↗