John Lightfoot on Luke 11:52

[Ye have taken away the key of knowledge.] Should we render it, Ye have taken the key of knowledge, (that is, to yourselves) or, Ye have taken it away; there is not much difference. They took the key of knowledge to themselves, when they arrogated to themselves only all profoundness of wisdom and learning, hereby indeed taking it away from the people, because they taught them nothing but trifling and idle stuff.

The word for key in their language brings to mind the word which was so very much in use amongst them for one that was teaching. Instances of this were endless: there are enough of it in that long preface prefixed to that Midras Threnorum, that hath for its title, The opening of the wise; where (as indeed almost everywhere else), it is so frequently said, R. such a one 'opened'; for I cannot tell how better to render it...