John Chrysostom

Then too he gives him to understand why, turning from him, he addressed his speech to the king: "For the king knoweth of these things, before whom also I speak freely: for I am persuaded that none of these things are hidden from him: for this thing was not done in a corner." He shows, that the king knows all perfectly; at the same time, all but saying to the Jews, And ye indeed ought to have known these things-for this is the meaning of that which he adds, "For this thing was not done in a corner."

Homily on Acts 52 ↗

Oecumenius

But Paul explains the reason for which he turned his speech to the king. Then, showing that this doctrine had become everywhere in the inhabited world, he added: "this has not been done in a corner," speaking about the cross and the resurrection of Christ.

Commentary on Acts ↗