Source: p 174, The Catholic Christian Instructed in the Sacraments ..., by Richard Challoner, 1786
Q. But does not Christ say, concerning continency, St. Matt. xix. 11,
'All men cannot receive this saving :' and St. Paul, I Cor. vii. 9,
'If they cannot contain, let them marry: far it is better to marry than to burn?'
A. No: both these texts are wllfully corrupted inthe Protestant Testament
. Where he speaks not of such as have vowed chastity, but of other Christians whom he advises rather to marry than to burn with unlawful lust here, and for unlawful lust hereafter
I guess that the relative pronoun Where refers to the Protestant Testament
in the preceding main clause, and he = Christ who is cited in the question. If so, why was this relative clause written as a separate clause, preceded by a comma? Why not join it to the previous main clause?
My guess: This dialogue reflects a conversation, so the relative clause may have been spoken only some time after the vocalisation of the main clause, but then I'd counter that the goal of clarity should prevail and so the clauses should be joined?
Footnote:
I lit on this work only while reading definition c. for 'to vow' on OED.