When He says here, “Knows not,” He means, ‘makes others not to know;’ i.e. He knew not then, so as to tell His disciples; as it was said to Abraham, “Now I know that thou fearest God;” [Gen 22:19] i.e. ‘Now have I caused that thou shouldest know,’ because by the temptation he came to know himself.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Trin., i, 12