Augustine of Hippo — as excerpted in the Catena Aurea on John 19:9-12

“(Tr. cxvi. 4) In comparing the accounts of the different Evangelists together, we find that this silence was maintained more than once; viz. before the High Priest, before, Herod, and before Pilate. So that the prophecy of Him, As a sheep before her shearers is dumb, so opened He not His mouth, (Isa. 53:7.) was amply fulfilled. To many indeed of the questions put to Him, He did reply, but where He did not reply, this comparison of the sheep shews us that His was not a silence of guilt, but of innocence; not of self-condemnation, but of compassion, and willingness to suffer for the sins of others.”