Chapter XII: Let them beware, as much as possible, of solemn oaths.

Let them abstain, moreover, from all solemn oaths, except as driven by necessity in the cases excepted through the indulgence of the Apostolic See, namely, on behalf of peace, the Faith, to hinder calumny and bear witness, and even in contracts regarding buying, selling, and donations, where it will seem expedient. Let them also avoid oaths in everyday speech, as much as they are able. And let him, who on any day has sworn less cautiously out of a slip of the tongue (as customarily happens in speaking much) that day at the fall of evening, when he ought to ponder what he has done, say three times the Lord's Prayer, on account of having recklessly made an oath of this kind. Moreover, let each be mindful, to exhort his own family to respect God's Name [divina obsequia].