A: The Second Commandment: Thou shalt not take the Name of God in vain, forbids us: (1) To utter the Name of God irreverently; (2) To blaspheme God, the Blessed Virgin or the Saints; (3) To take false, unnecessary, or unlawful oaths.
A: Not to utter the Name of God irreverently means not to mention this Holy Name, or any other name that in a special way refers to God Himself, such as the name of Jesus, of Mary and the Saints, in anger or in joke or in any irreverent way whatsoever.
A: Blasphemy is a horrible sin which consists in words or acts of contempt or malediction against God, the Blessed Virgin, the Saints, or sacred things.
A: There is a difference, because by blasphemy one wishes evil to or curses God, the Blessed Virgin or the Saints; while by imprecation one wishes evil to or curses one's self or one's neighbor.
A: An oath is the calling on God to witness the truth of what one says or promises.
A: It is not always forbidden to take an oath; an oath is lawful and even gives honor to God, when it is necessary, and when one swears with truth, judgment and justice.
A: When one affirms on oath what he knows or believes to be false, or when one promises under oath to do what one has no intention of doing.
A: When one makes oaths imprudently and without mature consideration, or in trivial matters.
A: When one makes an oath to do something unjust or unlawful, as, for example, to swear to take revenge, or to steal, and so on.
A: Not only are we not obliged, but we should sin by doing such things, because they are forbidden by the laws of God and of the Church.
A: He who swears falsely commits a mortal sin, because he grievously dishonors God, the Infinite Truth, by calling Him to witness what is false.
A: The Second Commandment commands us to honor the Holy Name of God as well as to keep our oaths and vows.
A: A vow is a promise made to God regarding something which is good, within our power, and better than its opposite, and to the keeping of which we bind ourselves just as if it had been commanded us.
A: Commutation or dispensation, may be sought from one's Bishop or from the Pope, according to the character of the vow.
A: It is a sin to break a vow and therefore we should not make vows without mature reflection, nor, as a rule, without the advice of our confessor or other prudent person, so as not to expose ourselves to the danger of sinning.
A: Vows are made to God alone; we may, however, promise God to do something in honor of our Lady or the Saints.