From The Divine Comedy: III. Paradise, Canto V, translated by Dorothy L. Sayers and Barbara Reynolds. Beatrice describes two cases of misguided men (Jepthah, in the Old Testament, and Agamemnon) who, by keeping their vows, caused grief. She warns, "Keep your oath / But not with stubborn wall-eyed foolishness." Then she goes on to say:
Christians, be steadier in what you do,
Not blown like feathers at the wind's discretion,
Nor think that every water cleanses you;
You have both Testaments in your possession,
You have the Shepherd of the Church for guide;
So let these things suffice for your salvation...
Behave like men, and not like witless sheep...