He did not therefore need to pray: He prayed for our sakes, that we might know Him to be the Son: But because of the people which stand by I said it, that they may believe that Thou hast sent Me. His prayer did not benefit Himself, but benefited our faith. He did not want help, but we want instruction.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: lib. x. de Trin.