In the Old Testament
To swear is to assert as true under oath. Those who serve God in spirit and in truth will not indulge in casual swearing or any careless language. The third commandment states, “You shall not take the name of the Lord your God in vain, for the Lord will not hold him guiltless who takes his name in vain” (Exodus 20:7). God’s children will avoid any irreverent, or unnecessary use of His holy name in swearing. Lying under oath is considered a most serious crime, because it perverts justice and therefore, deserves divine punishment (Matthew 5:33–37).
The Lord clearly instructed, “You shall not swear by my name falsely, and so profane the name of your God: I am the Lord” (Leviticus 19:12). This command is not concerned with swearing in court but with swearing falsely. The wise man said, “Put away from you crooked speech, and put devious talk far from you” (Proverbs 4:24).
David wrote that casual swearing is the language of the wicked (Psalm 10:7). Angry words show that pride and self-will fill the heart. God’s children must set a watch upon their lips (Psalms 141:3). They should seek the Lord to cleans their tongues (Psalms 101:5; Proverbs 6:12).
In the New Testament
About swearing Christ said, “you have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn.’ But I say to you, Do not take an oath at all, either by heaven, for it is the throne of God, or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great King. And do not take an oath by your head, for you cannot make one hair white or black. Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil” (Matthew 5:33-37). In this passage, Christ refers, not to the solemn judicial oath (Matthew 26:64) but to the oaths that were common among the Jews. For Christ Himself answered under oath Before Caiaphas (Matthew 26:63, 64). Likewise, Paul repeatedly invoked God as witness that what he said was true (2 Corinthians 1:23; 11:31; 1 Thessalonians 5:27).
Christ taught, “The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks” (Luke 6:45). And He added, “what comes out of the mouth” is what “defiles a person” (Matthew 15:11). Therefore, Christ warned that for “every idle word men may speak, they will give account of it in the day of judgment” (Matthew 12:36,37).
Moved by this same principle, the apostle Paul taught the Colossians “you must put them all away: anger, wrath, malice, slander, and obscene talk from your mouth” (Colossians 3:8). Swearing, profanity and obscene conversation, have no place in the Christian’s life. They are the signs of an unconverted heart. Therefore, Paul exhorted the believers, “Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear” (Ephesians 4:29). And he admonished them, “Let there be no filthiness nor foolish talk nor crude joking, which are out of place, but instead let there be thanksgiving” (Ephesians 5:4).
Also, the apostle James reiterated the same truth about swearing, “But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation” (James 5:12). And he stated that the tongue is the hardest member to control (James 3:1–12). Only purity of mind and a close watch upon the tongue will eventually subdue the evil of the tongue.
Swearing and unsanctified speech show a mind still filled with earthy interests. But he who bridles his tongue and offends not in word, “the same is a perfect man” (James 3:2). So, James concluded, “If anyone thinks he is religious and does not bridle his tongue but deceives his heart, this person’s religion is worthless” (James 1:26).
There is hope for those that are commonly tempted to swear. Through the power of God, they can overcome the sins of the tongue. And they can be purified by the Holy Spirit to reflect the character of their Creator. “But thanks be to God! He gives us the victory through our Lord Jesus Christ” (1 Corinthians 15:57).
In His service,