Sentence:  And yet there is at Alexandria a fair church, all white without paintures; and so be all the other churches that were of the Christian men, all white within, for the Paynims and the Saracens made them white for to <WSD>fordo</WSD> the images of saints that were painted on the walls. 
Meaning of the word marked with <WSD> tags:  To do away with, undo; to ruin.