When Jesus taught his followers to let their “yes” mean yes and their “no” mean no, he was telling them to stop playing games with the truth. In his day, religious leaders had created loopholes that let people make oaths they didn’t really have to keep. Jesus cut through all of it. His followers should be so consistently honest that they never need an oath to prove they’re telling the truth.
The Original Purpose of Oaths
In the Sermon on the Mount, Jesus made six contrasts between how God’s law was commonly understood and what God really intended. The fourth deals with oaths. Jesus wasn’t talking about bad language. He was talking about swearing by something to prove we’re serious, like saying “I swear on my mother’s grave” or “Cross my heart.”
Oaths have a place in the Bible. God’s law required people to keep the vows they made.
Numbers 30:2 When a man makes a vow to the Lord or takes an oath to obligate himself by a pledge, he must not break his word but must do everything he said.
The purpose of an oath was to hold yourself accountable to God for telling the truth and keeping your promises. Even the apostle Paul called on God as his witness (2 Corinthians 1:23), and God himself swore by his own name to assure his people that he would keep his promises (Hebrews 6:13).
How Oaths Became Loopholes
Over time, religious leaders created a complicated system of rules about which oaths were binding and which weren’t. Jesus called it out directly.
Matthew 23:16-17 Woe to you, blind guides! You say, ‘If anyone swears by the temple, it means nothing; but anyone who swears by the gold of the temple is bound by that oath.’ You blind fools! Which is greater: the gold, or the temple that makes the gold sacred?
This system turned oaths into a game. It let people sound sincere while quietly leaving themselves a way out, like a child crossing his fingers behind his back. Swearing by heaven, earth, or Jerusalem also treated created things as if they could guarantee the truth, when only God can do that. A system meant to reinforce honesty had become a tool for deception.
Just Tell the Truth
Jesus’ answer was simple. Instead of debating which oaths count, just be honest every time you speak.
Matthew 5:37 All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one.
Jesus wasn’t necessarily banning every formal oath, like testifying in court. He was telling us not to play games with the truth. James repeated the same teaching: “All you need to say is a simple ‘Yes’ or ‘No.’ Otherwise you will be condemned” (James 5:12). An oath can’t make a liar honest anyway. Peter swore an oath when he denied knowing Jesus (Matthew 26:72). Our everyday words should be trustworthy enough that no oath is needed.
Our Honesty Points to a Trustworthy God
Telling the truth matters for more than our reputation. It affects how people see God. The Bible describes God as completely trustworthy.
Numbers 23:19 God is not human, that he should lie, not a human being, that he should change his mind. Does he speak and then not act? Does he promise and not fulfill?
God never breaks his word, and his promises are an anchor for our souls (Hebrews 6:19). But why would people believe God’s promises if they can’t believe ours? When Christians cut corners with the truth, exaggerate, or make promises we don’t keep, we make it harder for people to trust the God we represent. When our yes means yes, our lives point people to a faithful God.
The Takeaway
What did Jesus mean by “Let your yes be yes”? He meant that his followers should stop playing games with the truth. Instead of relying on oaths or loopholes, simply say what you mean, keep your word, and reflect the faithfulness of God.
