"A Dim Religious Light"

Context: John Milton, waking from a dream, wants to hear sweet music sent to him by a benevolent being such as a Genius, or presiding spirit, of the woods. He wishes never to depart from the cloisters of the student–perhaps a reference to Cambridge University. He wants always to love the high-arched roof, perhaps referring to that of King's College Chapel, which had the most beautiful interior of any building in England. He refers to pillars that are proof in their massiveness against destruction, and comments on stained-glass windows decorated with scenes from sacred history. Bernard Flower's twenty-five windows (1515-1531) of King's College Chapel depict the life of the Virgin and scenes from the Old Testament. They shed a subdued, many-colored light conducive to religious reflection. The passage is:

And as I wake, sweet music breathe
Above, about, or underneath,
Sent by some spirit to mortals good,
Or th'unseen Genius of the wood.
But let my due feet never fail
To walk the studious cloisters' pale,
And love the high embowéd roof,
With antic pillars massy proof,
And storied windows richly dight,
Casting a dim religious light.