A question whether it can be without sin that our knowledge affords to weak brethren an opportunity for lying.
Germanus: As far as the force of the words which have been reasonably and carefully considered, is concerned, our scruple about our promise would have easily been removed from us were it not that we were terribly alarmed lest by this example an opportunity for lying might be offered to certain weaker brethren, if they knew that the faith of an agreement could be in any way lawfully broken, whereas this very thing is forbidden in such vigorous and threatening terms by the prophet when he says: “You shall destroy all those who utter a lie;” and: “the mouth that speaks a lie, shall slay the soul.”
Source: Conferences (New Advent)