This is part of my commentary series on The 39 Articles of Religion. Article 39 states:
XXXIX. Of a Christian man’s Oath
As we confess that vain and rash Swearing is forbidden Christian men by our Lord Jesus Christ, and James his Apostle, so we judge, that Christian Religion doth not prohibit, but that a man may swear when the Magistrate requireth, in a cause of faith and charity, so it be done according to the Prophet’s teaching, in justice, judgement, and truth.
As with the previous Article, this final 39th Article addresses an issue of civil life which had been raised in the Anabaptist tradition: they refused to swear oaths of any kind. Following the New Testament passages alluded to in this Article (Matthew 5:33-37 and James 5:12) they concluded that Christians were not allowed to swear any sort of oath, including the standard oath to speak the truth in a court of law. To this day, certain religious traditions refuse to participate in that standard practice. Countering this, Article 39 cites “the Prophet’s teaching” from Jeremiah 4:2, which says “and if you swear, ‘As the Lord lives,’ in truth, in justice, and in righteousness, then nations shall bless themselves in him, and in him shall they glory.” Thus, it is quite permissible for us to comply with civil law and custom concerning solemn oaths – whether it’s swearing to tell the truth in the court or “swearing in” to a public office.
What is taught against, in this Article, is “vain and rash Swearing”. The most basic application of this is the 3rd Commandment: we are not to take the Lord’s name in vain. That is the usual biblical meaning of swearing – thoughtlessly using the name of God to back up something we say or promise, or simply using God’s name as a mere exclamation. All of that is sin, and therefore “is forbidden”.
All in all, this is a simple Article of faith. We are to mean what we say, and say what we mean. The sacred names of God are holy, and we are to speak of him and invoke his name only “in justice, judgement, and truth.” If we do so off-the-cuff, as it were, we are very likely being rash and falling into sin. But a considered promise or appeal to God’s name, such as those we make at Holy Baptism or Confirmation, is entirely in line with biblical teaching about Christian conduct and speech.