John Chrysostom

And Philip ran thither to him, and heard him reading; even the fact of his running, showed that he wished to say something. And the place of the Scripture which he read was this: As a sheep He was led to the slaughter. And this circumstance, also, is a token of his elevated mind, that he had in hand this prophet, who is more sublime than all others. Philip does not relate matters to him just as it might happen, but quietly: nay, does not say anything until he is questioned.

Homily on Acts 19 ↗

Cyril of Jerusalem

He is called a sheep; not a senseless one, but that which cleanses the world from sin by its precious blood, and when led before its shearer knows when to be silent.

Catechetical Lecture 10.3 ↗

Theophylact of Ohrid

"Like a sheep, He was led to the slaughter." The meaning of the words cited is very clear, because at a certain time sheep are led away for shearing and the shepherds lay upon them the instruments of shearing, yet the sheep endure this and do not attack those who do it. So also Christ, enduring reviling, did not repay reviling for reviling.

Commentary on Acts ↗

Bede

And as a lamb before its shearer is silent. He not only redeemed us with his blood but also covered us with his wool, so that we, shivering in our unbelief, might be warmed by his garment, and we might hear the Apostle speaking to us: As many of you as were baptized into Christ have put on Christ. Thus, he did not open his mouth, since in his passion he wished to answer Pilate and the chief priests briefly, and Herod not at all.

Commentary on Acts ↗