What does the Church teach regarding oaths?

In His Sermon on the Mount, as recorded in the Gospel of St. Matthew, our Lord taught, “You have heard the commandment imposed on your forefathers, ‘Do not take a false oath; rather, make good to the Lord all your pledges.’  What I tell you is: do not swear at all.  Do not swear by Heaven (it is God’s throne), nor by the earth (it is His footstool), nor by Jerusalem (it is the city of the great King); do not swear by your head (you cannot make a single hair white or black).  Say, ‘Yes’ when you mean ‘Yes’ and ‘No’ when you mean ‘No.’  Anything beyond that is from the evil one” (Matthew 5:33-37).  Later, St. James in his letter repeated this precept: “Above all else, my brothers, you must not swear an oath, any oath at all, either ‘by Heaven’ or ‘by earth.’  Rather let it be ‘yes’ if you mean yes and ‘no’ if you mean no” (James 5:12).

To understand fully our Lord’s teaching, we must first appreciate the Old Testament teaching concerning oaths.  The Eighth Commandment clearly mandates the telling of truth: “Thou shalt not bear false witness against thy neighbor” forbids any misrepresentation of the truth.  However, while lying is a sin in itself, the gravity of the sin is intensified when one has asked God to bear witness to false testimony.  For example, the Old Testament highlights the importance of truthfulness when God has been called as a witness:  “When a man makes a vow to the Lord or binds himself under oath to a pledge of abstinence, he shall not violate his word, but must fulfill exactly the promise he has uttered” (Numbers 30:3) and “When you make a vow to the Lord, your God, you shall not delay in fulfilling it; otherwise you will be held guilty, for the Lord, your God, is strict in requiring it of you. …But you must keep your solemn word and fulfill the votive offering you have freely promised to the Lord” (Deuteronomy 23:22, 24).

Couple this teaching with the Second Commandment, “Thou shalt not take the name of the Lord thy God in vain.”  A person who invokes God’s name in witnessing the telling of the truth when in fact he is lying, not only lies but blasphemes God.  Clearly, the people of the Old Testament understood the obligation to tell the truth as faithful members of the covenant, and appreciated the solemnity of God’s witness and judgment to testimony under oath.

At the time of our Lord, the Jewish people had maneuvered around the strict precepts regarding oaths.  If one actually invoked the Lord to bear witness to the truth, then that oath was absolute.  However, if one invoked the temple, Heaven, earth, one’s head, or something else, the oath could be broken.  A casuistry evolved whereby depending upon by what thing one swore determined how easily the oath could be broken.  For this reason, our Lord castigated the Pharisees, “Again you declare, ‘If a man swears by the temple it means nothing, but if he swears by the gold of the temple he is obligated.’  Blind fools!  Which is more important, the gold or the temple which makes it sacred?  Again you declare, ‘If a man swears by the altar it means nothing, but if he swears by the gift on the altar he is obligated.’  How blind you are!  Which is more important, the offering or the altar which makes the offering sacred?  The man who swears by the altar is swearing by it and by everything on it.  The man who swears by the temple is swearing by it and by Him who dwells there” (Matthew 23:16-21).  Clearly, our Lord rejected the legal hair-splitting, the verbal gymnastics, and the whole casuistry and asserted, “Say ‘yes’ when you mean yes and ‘no’ when you mean no.”  In essence, the faithful member of the Church should always be truthful, since the Lord Himself is Truth.

Why then should we take oaths or still require the taking of oaths?  Perhaps we do so because we are the poor victims of original sin and such an oath reminds us of the need to be truthful and of the witness of God.  After all, St. Paul even invoked the Lord to witness speech:  “I swear by the Christ who is in me…” in writing to the Corinthians (II Cor 11:10); and “The God  I worship in the spirit by preaching the gospel of His Son will bear witness that I constantly mention you in prayer” (Romans 1:9).  While the oath does not guarantee truthfulness of the individual (for he could still lie), it does show his submission to the Lord’s witness and judgment.

Our Church requires the taking of oaths:  Before a bishop is ordained or takes formal possession of his diocese, he must make a profession of faith and take an oath of fidelity to the Apostolic See, i.e. the Holy Father (Code of Canon Law, #381).  Candidates for the priesthood do the same.  Teachers of theology in Catholic colleges and universities, since they share in the mission of the Magisterium, ought to take an oath of fidelity to it each year.

Consequently, the Catechism states the traditional interpretation of the Sermon on the Mount that Jesus did not exclude oaths made “for grave and right reasons” (#2153), but rather condemned  false and frivolous oaths.  Here the Catechism again underscores the point that since “taking an oath or swearing is to take God as witness to what one affirms” (#2150), a false oath asks God to witness, a lie, which is an act of blasphemy.  God’s presence and His truthfulness must always be respected; otherwise, we mock Him.

Therefore, an oath must only be taken in truth, in justice, and in judgment (Code of Canon Law, #1199).  “In truth” means that the person is not lying and has moral certitude to the facts asserted; a person cannot take an oath who is doubtful about the matter at hand.  “In justice” means that nothing unlawful must be asserted or promised in the oath, such as swearing to commit murder.  Finally, “right judgment” attests that there is sufficient cause for invoking God to witness the oath and that this is done with reverence.

In all, our Lord demands truthfulness.  Truthfulness is simply part of genuine Christian integrity.  To lie, and especially to lie under oath, causes scandal to both believers and non-believers alike and jeopardizes the soul of the person.

Remember the scene from the movie A Man for All Seasons (based on the play by Robert Bolt), in which St. Thomas More speaks with his daughter Margaret about taking the Oath prescribed by the Act of Succession, which asserted that Henry VIII was the lawful head of the Church, that Anne Boleyn was the rightful queen, and that her children were the legitimate heirs to the throne.  St. Thomas explains to his daughter why he cannot take the oath in good conscience:  “What is an oath then, but what words we say to God?  When a man takes an oath he is holding his own self in his own hands, like water.  If he opens his fingers then, he needn’t hope to find himself again.”   In the end, St. Thomas More died for the truth.  How tragic it is in our world today when individuals lie under oath  and then refuse to admit they have lied.  Moreover, how sad it is when those individuals entrusted to uphold the law fail to protect what is truthful, right, and just by making light of the transgression or legitimizing the breaking of the oath by certain circumstances.  Christians must live, promote, and defend the truth as did St. Thomas More.