Once again quoting from Carolyn Weber's wonderful memoir, Surprised by Oxford. This quote came from a discussion in one of her Oxford literature classes after a student asked the professor why they had to do memory work.
"Consider how easy you have it,' he replied. "Many of the Romantics knew much of Milton by heart – how can you study these writers if you do not know what was in their hearts as they themselves wrote?' Then he added, thoughtfully, 'While you are at it, I also suggest that you memorize the first few chapters of Genesis. So you know what was in Milton's heart too.'
'Why memorize it? Why not just read it carefully?' argued Susan, our Yale
'Because what you memorize by heart, you take to heart,' replied Dr Nuttham simply. "It shouldn't be called by 'rote' but by 'root', for you get at the source of the text, its foundation. Once you really absorb the words, the words become you own. Then, and only then, can you mull them over on your tongue, appreciate them as you would good wine, enjoying them as the company of a good friend. Besides,' he added, 'we always value something for which we've had to labor."
~Carolyn Weber, Surprised by Oxford