The Hebrew prophet Elijah was sent into hiding and fed by ravens. The episode had a great personal significance for Defoe.
And the word of the LORD came unto him, saying, "Get thee hence, and turn thee eastward, and hide thyself by the brook Cherith, that is before Jordan. And it shall be, that thou shalt drink of the brook; and I have commanded the ravens to feed thee there."
So he went and did according unto the word of the LORD: for he went and dwelt by the brook Cherith, that is before Jordan. And the ravens brought him bread and flesh in the morning, and bread and flesh in the evening; and he drank of the brook.
1 Kings 17:2-6