Isobel wrote:
>>  Where can I find some information on the
>> significance of the numbers 7 and 12 in medieval religious literature?

One important source of symbolic sevens and twelves was of course the book
of Revelation (or the Apocalypse), which is full of them:  seven seals,
seven angels, seven trumpets, etc., and twelves and multiples of twelve esp.
in the 144,000 redeemed souls and the New Jerusalem , with its twelve gates
(each named for one of the twelve tribes of Israel), twelve foundation
stones (each named for one of the twelve apostles) faced with twelve
different gems, the city's dimensions expressed in multiples of twelve, and
so on.  

So one place I'd look for interpretations of these numbers would be the
standard medieval commentaries on this part of the Bible.

Sherry Reames