Heidelberg Catechism: Lord's Day 37

This week, the Heidelberg Catechism asks an important question: what about oaths? Are Christians ever permitted to swear, or does faithfulness to Christ require that we avoid such promises altogether?

Question 101

But may we swear an oath in God's name if we do it reverently?

Yes, when the government demands it, or when necessity requires it, in order to maintain and promote truth and trustworthiness, for God's glory and our neighbor's good. Such oath-taking is grounded in God's Word and was rightly used by saints in both the Old and New Testaments.¹

¹ Deuteronomy 6:13; Jeremiah 4:2; Hebrews 6:16; 2 Corinthians 1:23

Question 102

May we also swear by saints or other creatures?

No. A lawful oath is a calling upon God, who alone knows the heart, to bear witness to the truth and to punish me if I swear falsely. No creature is worthy of such honor.²

² Matthew 5:34–37; James 5:12

The Apparent Tension

At first glance, oaths may feel out of step with the simplicity Jesus commends when He says, "Let your 'yes' be yes and your 'no' be no" (Matthew 5:37). Doesn't all oath-taking go beyond this? In Jesus' teaching, He warns against the elaborate oath-making of His day, where people swore "by heaven," "by the temple," or "by Jerusalem" to add weight to their words (Matthew 23:16-22).

So why does the Catechism affirm that oaths can be lawful and even necessary? The answer lies in understanding what Jesus opposed and what Scripture affirms.

What Jesus Opposed

Jesus wasn't condemning all oaths. He was exposing the manipulative oath-making of the religious leaders. They had created a complex system where some oaths were binding and others were not (Matthew 23:16-18). People could swear by the temple but not feel bound by it, yet swearing by the gold of the temple was considered binding. This turned truth-telling into a legal game where clever word-choice could mask deception.

The heart of Jesus' concern was that people were using oaths as substitutes for consistent truthfulness, rather than as solemn confirmations of it.

What Scripture Affirms

The Catechism reminds us that God Himself confirms His covenant with oaths (Hebrews 6:16-18; Genesis 22:16). When Abraham received God's promise, "God desired to show more convincingly to the heirs of the promise the unchangeable character of his purpose" by adding an oath (Hebrews 6:17). Paul, too, called God as his witness in solemn moments (2 Corinthians 1:23; Romans 1:9).

Scripture reveals that oaths, rightly used, are good gifts of God. They solemnize truth, establish trust, and give weight to promises that shape society (Deuteronomy 10:20; Psalm 15:4). When we take an oath reverently—whether in a courtroom, at a wedding, or in a solemn vow of office—we are acknowledging that our words are spoken before the face of God. We bind ourselves before the courts of heaven and earth.

The Heart of the Matter: Truthfulness

Behind the Catechism's teaching on oaths lies a call to consistent truthfulness. The Christian life should not be a performance where honesty appears only under oath. Instead, we are called to live every day as those whose words reflect the God of truth (Numbers 23:19; Titus 1:2).

This is why both Jesus and James press us toward simplicity in speech (James 5:12). Our ordinary words should be so trustworthy that an oath, when required, is simply a formal recognition of what is already true about our character. In this sense, lawful oaths are not escapes from everyday honesty but confirmations of a pattern already evident.

The Danger of Misplaced Trust

The Catechism's second question addresses another crucial point: we must swear only by God's name, never by created things or people (Matthew 5:34-37). Why? Because only God knows the heart completely (1 Kings 8:39), and only God has the authority to judge our faithfulness to our words (Romans 14:12).

In our day, we may not swear "by Jerusalem," but we often invoke human institutions, cultural symbols, or even our own reputations to give credibility to our words. Yet all of these fall short. To swear rightly is to entrust our words to God's judgment and our promises to His sustaining grace (Philippians 4:13).

A Gospel Word on Promises

How can we live as people of truth when our words so often falter? The good news is that our hope does not rest on the strength of our promises but on the faithfulness of God's promises (2 Timothy 2:13). Every broken vow we have made is covered by the unbreakable covenant sealed in Christ's blood (Hebrews 9:15).

The gospel does not merely pardon us for false words; it reshapes us into people who reflect God's own reliability (2 Corinthians 3:18). Because Christ is the "Yes" and "Amen" of every divine promise (2 Corinthians 1:20), those united to Him can begin to speak with integrity, even in a world of deception (Ephesians 4:25).

A Closing Prayer

Faithful God, You are the God of truth, and every promise You make stands forever (Isaiah 55:11). Forgive me for careless words, half-kept commitments, and broken promises. Thank You that Jesus Christ fulfilled every oath and bore the guilt of my falsehoods. Teach me to speak with integrity, to keep my word, and to honor Your name in all my promises (Psalm 15:1-4). And when I am called to swear an oath, let me do so reverently, for Your glory and my neighbor's good. Through Jesus Christ, the Amen to all Your promises, I pray. Amen.

Daily Bible Readings

New Testament in a Year
September 14 – John 6:60–71
September 15 – John 7:1–24
September 16 – John 7:25–53
September 17 – John 8:1–30
September 18 – John 8:31–59
September 19 – John 9:1–23
September 20 – John 9:24–41

The Bible in a Year
September 14 – Song of Solomon 1–3; John 6:60–71
September 15 – Song of Solomon 4–5; John 7:1–24
September 16 – Song of Solomon 6–8; John 7:25–53
September 17 – Isaiah 1–2; John 8:1–30
September 18 – Isaiah 3–4; John 8:31–59
September 19 – Isaiah 5–6; John 9:1–23
September 20 – Isaiah 7–8; John 9:24–41