In many conversations today, marital faithfulness is reduced to what one doesn’t do. But for John Calvin, that standard misses the point. Calvin believed marriage calls for more than avoiding infidelity—it requires undivided commitment in thought, affection, and intention. For him, what happens in the heart matters as much as any action. This lens reframes […]
In many conversations today, marital faithfulness is reduced to what one doesn’t do. But for John Calvin, that standard misses the point. Calvin believed marriage calls for more than avoiding infidelity—it requires undivided commitment in thought, affection, and intention. For him, what happens in the heart matters as much as any action. This lens reframes not only physical betrayal but emotional entanglements and quiet compromises. So what can Calvin’s 16th-century insights teach us in an era marked by open relationships, private DMs, and eroding trust? A lot more than we might expect.
Calvin didn’t view marriage as a contract to be broken when it stops being convenient.1 He saw it as a covenant—binding and holy—made before God, not just friends and family. In his mind, the relationship between a husband and wife mirrors a spiritual reality. When two people marry, they’re not forming a partnership for mutual benefit. They’re entering into something sacred, accountable to God Himself. Break that bond—even internally—and you don’t just betray a spouse. You betray the One who instituted the union.
Referencing Genesis 2:24, Calvin took the phrase “one flesh” seriously.2 That unity wasn’t limited to physical connection. It extended to the mind, emotions, and will. When someone pulls their affection away—through wandering thoughts, emotional attachments, or neglect—they’re dismantling what was meant to be whole. Calvin didn’t mince words: even private betrayal violates the nature of marriage. If spouses are truly joined, then divided hearts are more than just a struggle—they’re a contradiction of what marriage is.
For Calvin, the seventh commandment wasn’t just about physical boundaries. He saw it as a call to inward integrity. Lustful thoughts, suggestive glances, and quiet fantasies weren’t harmless—they were violations of God’s intent.3 He argued that when someone stirs up desire for someone outside their marriage—even in imagination—they’ve already crossed a line.4
Today, we might call it an “emotional affair.” Calvin wouldn’t bother with the label. He’d call it betrayal. Cultivating a secret bond—sharing affections, vulnerabilities, or flirtations meant for one’s spouse—is, in his framework, a clear violation. The body may stay loyal, but the heart has already moved.
Calvin warned against patting yourself on the back for staying out of bed with someone who isn’t your spouse while letting your imagination run wild. Abstaining from the act doesn’t excuse indulgence in fantasy. To him, a person might appear upright while their mind is tangled in lust—and that’s not chastity. That’s self-deception.
Referencing 1 Corinthians 7:34, he insisted that holiness must touch both body and spirit.5 It’s not just about saying no to external temptation. It’s about refusing to entertain desire that doesn’t belong. Fantasizing, flirting with someone emotionally, or chasing after a bond outside of marriage all fall short of the purity God expects.
If you want to stay faithful, don’t wait for temptation to knock—cut off the access. Watch what you let your eyes linger on. Don’t dress to provoke attention that isn’t meant for your spouse. Clean up your speech. Don’t let your cravings—sexual or otherwise—train your mind toward indulgence.6
Calvin linked purity to sincerity. He pointed to Jesus’s words in Matthew 5:8: “Blessed are the pure in heart.” That purity, he said, shows up not just in what you do—but in whether your words and expressions reflect what’s really going on inside.7
For Calvin, betrayal didn’t begin in a bedroom or end in a courtroom. It started when someone divided their affections—when one person stopped being “one” with another in heart, will, and intention. He read Malachi 2 as a warning: when you turn your back on your spouse, you’re turning your back on the One who joined you.8
Calvin pushed deeper: faithfulness isn’t just about avoiding the wrong thing—it’s about actively offering love, affection, and care to your spouse. If you withhold love, or treat your spouse as a means to an end, you’ve missed the point.9
Calvin had no patience for appearances. He argued that it’s better to end a marriage than to pretend to honor it while emotionally investing elsewhere. In his commentary on polygamy, he didn’t just condemn adding a second partner—he condemned the cruelty of staying with the first while giving yourself to another.10
The internet has made emotional betrayal easier to rationalize and harder to detect. A late-night text, a private DM, a string of heart emojis—none of it seems like much. But Calvin wouldn’t be fooled. He would see right through the illusion of innocence. If your emotional intimacy with someone else takes the place your spouse should hold, it’s sin. Period.
For Calvin, the answer isn’t shame—it’s repentance. He wouldn’t just call out sin; he’d call people back. He’d point to James 4:8: “Purify your hearts, you double-minded.” The solution to a divided heart isn’t hiding. It’s confession. And a return to wholeness.
Calvin didn’t hold up impossible standards just to leave us crushed. He believed that Christ came for the broken, the unfaithful, the conflicted. That includes anyone whose heart has wandered—even if their marriage never technically ended.
The gospel doesn’t just forgive. It restores. Calvin saw God’s grace not as a loophole, but as power.11 Power to change. Power to live in integrity again. The same grace that covers betrayal equips us to love rightly, speak truthfully, and offer undivided loyalty again.12
This isn’t just about marriage. It’s about integrity before God. Calvin’s theology of faithfulness speaks to anyone who’s tempted to live in halves—half-in a relationship, half-devoted, half-truthful. He didn’t leave room for that. And neither should we.
In a culture that cheapens commitment and rebrands self-centeredness as liberation, Calvin calls us back to something deeper: covenant. Wholeness. A heart that belongs fully to one, and is watched over by God.