An oath has been defined as “a solemn, formal declaration or promise to fulfill a pledge, often calling on God . . . as witness.” It may be oral or written.

Some may think that it is wrong to take an oath because Jesus said: “Do not swear [an oath] at all . . . Just let your word ‘Yes’ mean yes, your ‘No,’ no, for what goes beyond these is from the wicked one.” (Matt. 5:33-37) Of course, Jesus knew that the Mosaic Law required certain oaths and that faithful servants of God had made sworn oaths. (Gen. 14:22, 23; Ex. 22:10, 11) He also knew that Jehovah himself swore oaths. (Heb. 6:13-17) So Jesus could not have meant that we should never take an oath. Rather, he was warning against taking oaths that are trivial or meaningless. We should view the keeping of our word as a sacred duty. We must mean what we say.

What, then, should you do if you are asked to swear an oath? First, make sure you can do what you swear to do. If you are not sure, it would be best that you not take the oath. God’s Word warns: “Better for you not to vow than to vow and not pay.” (Eccl. 5:5) Next, consider Scriptural principles that relate to the oath, and then act in harmony with your trained conscience. What are some of these Scriptural principles?

Some oaths are compatible with God’s will. For example, Jehovah’s Witnesses exchange vows when being joined in marriage. These vows are a type of oath. Before God and eyewitnesses, the bride and the groom promise that they will love, cherish, and respect each other and that they will do so “for as long as [they] both may live.” (Other couples may not say these exact words when they marry, but they still make a vow before God.) They are then pronounced husband and wife, and their marriage is meant to be a lifelong bond. (Gen. 2:24; 1 Cor. 7:39) This arrangement is proper, fitting, and in harmony with God’s will.

Some oaths are in conflict with God’s will. A true Christian would not take such an oath as to defend a country with arms or to renounce faith in God. Doing so would violate God’s commandments. Christians are to be “no part of the world,” so we cannot get involved in its controversies and conflicts.​—John 15:19; Isa. 2:4; Jas. 1:27.

Some oaths are a matter of conscience. At times, we may need to evaluate an oath carefully in the light of Jesus’ counsel to  “pay back Caesar’s things to Caesar but God’s things to God.”​—Luke 20:25.

Suppose, for example, that a Christian applies for citizenship or for a passport and he learns that he is required to take an oath of allegiance. If in that country such an oath means swearing to act in a way clearly contrary to God’s law, his Bible-trained conscience would not allow him to take it. The government, however, may allow him to modify the wording of the oath to accommodate his conscience.

Taking a modified oath of allegiance may be in harmony with the principle found at Romans 13:1, which says: “Let every person be in subjection to the superior authorities.” So the Christian may decide that there is nothing objectionable about swearing to do something that God already obligates one to do.

Conscience also plays a role if you are asked to use an object or to make a gesture while swearing an oath. The ancient Romans and Scythians swore by their swords, invoking the power of a war god as a guarantee of the person’s trustworthiness. The Greeks raised a hand to heaven when taking an oath. They thus recognized that there is a divine power who observes what is said and what is done and to whom humans are accountable.

Of course, a servant of Jehovah would not swear on any national emblem connected to false worship. But what if you are asked in a court of law to place your hand on a Bible and swear to give truthful testimony? In that case, you may decide to do so, since the Scriptures tell of faithful ones who accompanied an oath with a gesture. (Gen. 24:2, 3, 9; 47:29-31) It is important to remember that if you take such an oath, you are swearing before God that you will tell the truth. You need to be prepared to answer truthfully any question that may be asked of you.

Because we treasure our relationship with Jehovah, we should prayerfully consider any oath we are asked to take, making sure that it will not violate our conscience or Bible principles. If you decide to take an oath, you must be sure to keep it.​—1 Pet. 2:12.