By the sitting we must not conceive a posture of the human limbs, as if the Father sat on the left and the Son on: the right, but the right hand itself we must interpret to be the power which that Man received who was taken up into Himself by God, that He should come to judge, who at first came to be judged.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Symbolo. ad Catech. l. ii. c. 7.