A caballo regalado no le mires el diente.

A caballo regalado no le mires el diente Don’t look at the tooth of a gifted horse. Don’t appraise the value of what you’ve been given.

A horse trader’s eye, examined closely, will keep returning to one place. It is not the legs and not the chest and not the coat. It is the mouth. A horse’s incisors and molars wear in a predictable enough pattern that an experienced buyer can estimate the animal’s age, almost to the year, by the angle of the teeth and the depth of the cups along the biting surface. The phrase to look at a horse’s teeth — mirar el diente, guardare in bocca — is, across most of Europe, a single semantic gesture. It means: to evaluate. It means: to find out what you are getting.

The proverb forbids exactly this gesture. A caballo regalado no le mires el diente. Don’t look at the tooth of a gifted horse. Don’t open the mouth. Don’t run the appraisal. Don’t, in the moment of receiving a gift, become a buyer.

This is one of the most-traveled proverbs in the European archive. It exists, in close variants, in Latin, Italian, Spanish, French, German, Polish, Russian, English. The image is the same in every version. What is interesting about the saying is what is interesting about most heavily-migrated proverbs: the small differences that survive the migration tell you something about the cultures that preserved them.

What it means

The literal Spanish is plain. A caballo regalado — to a gifted horse. No le mires el diente — don’t look at its tooth (singular). The instruction is a negative imperative; the proverb is teaching, not just observing.

Idiomatically, the saying applies to any received thing. A handed-down winter coat. An apartment offered at below market rent by an aunt. A used car given by a parent. A favor done for you that was not as elegant as the favor you would have done yourself. The proverb asks the recipient to stop, mid-evaluation, and recognize that evaluation is not the appropriate response. The proper response is acceptance. The price tag is not visible because there isn’t one.

There is a subtler use, increasingly common in modern Spanish: ironic. A friend complaining about the brand of wine someone brought to a party may be told a caballo regalado no le mires el diente with a small smile. The complaint is being gently chided. The saying defangs ingratitude before it can become rudeness.

Where it comes from

The proverb is securely traceable to St. Jerome, the late-fourth-century Christian scholar best known for the Latin Vulgate translation of the Bible. In the prologue to his commentary on Paul’s Epistle to the Ephesians, Jerome writes Equi donati dentes non inspiciuntur — “the teeth of a gifted horse are not inspected” — using the saying as if it were already proverbial in his readers’ Latin. So the proverb is at least as old as the late Roman world; whether Jerome is quoting a saying that already had centuries of life behind it is hard to say, but the phrase has the worn smoothness of an established proverb rather than the angularity of a freshly minted one.

From Jerome’s Latin, the saying enters medieval European proverb collections as a stable tag and from there into the vernaculars. It crosses into Italian as a caval donato non si guarda in bocca, into Spanish as a caballo regalado no le mires el diente, into French as à cheval donné on ne regarde pas la bouche, into Russian as дареному коню в зубы не смотрят, into English as don’t look a gift horse in the mouth. The image — horse, mouth, evaluation — is preserved across every transmission. The grammatical mood and the precise inspected anatomy shift slightly from language to language. The horse stays a horse.

How it gets used today

Today the Spanish proverb is one of the most reliably current sayings in the language and travels easily across Latin American and peninsular Spanish. It appears in family settings — a Madrid mother chiding a child who has begun complaining about a hand-me-down — and in workplace settings, where it is used to discourage criticism of well-intentioned but imperfect contributions. It also has a particular life in commercial contexts, where it is sometimes pressed into ironic service against itself: a buyer haggling over the price of a “discounted” item may be reminded, by the seller, a caballo regalado, with the implication that the buyer should accept the offered price gratefully even though the transaction is not actually a gift. The proverb’s gentle blackmail-by-good-manners is part of how it survives.

In Latin American Spanish the proverb is no less current and is often paired with the further saying a falta de pan, buenas son tortas — “for lack of bread, cakes are good” — to soften any complaint about quality with the suggestion that the alternative is nothing at all.

Cousins from other tongues

The proverb is unusual for a European saying in that the cousin set is also the family tree. Each version preserves the same image with small shifts that say something about the version’s home culture.

The Latin original, Equi donati dentes non inspiciuntur, sets the template. Note the passive voice — are not inspected, not do not inspect — and the plural dentes, teeth. Jerome’s phrasing is impersonal; it states a rule of conduct rather than addressing a recipient. Latin’s preference for the passive in moral counsel gives the saying a slightly legal feeling. The proverb is not a friend reminding you. It is a statute being read out.

The Italian, a caval donato non si guarda in bocca, is the closest sibling to the Spanish, with one telling difference. The Italian inspects in bocca — in the mouth; the Spanish inspects el diente — the tooth. The Italian generalizes; the Spanish specifies. The Spanish proverb has zoomed in on the precise place the appraiser would look. The Italian leaves it implied. There is an Italian preference, throughout the language’s idiomatic register, for slightly more spacious imagery; the Spanish prefers, often, the cleanly named anatomical detail. El diente is closer to the gum line. In bocca is closer to the room.

The Russian, дареному коню в зубы не смотрят — darenomu konyu v zuby ne smotryat, “they don’t look at the teeth of a gifted horse” — keeps the plural teeth of the Latin, but recovers the Italian’s to construction (в зубы — into the teeth). What is most interesting about the Russian version is its register. In Russian, horses were until very recently a primary work animal and a measure of household wealth in a way they had stopped being in much of Western Europe by the time the proverb stabilized. The Russian saying retains a slightly heavier weight. A gift horse, in 19th-century Russian usage, was not a metaphor. It was a horse. The proverb’s caution against ingratitude was correspondingly less abstract: someone had genuinely just given you an animal that could pull a cart, and you were being asked, sharply, not to start checking it for soundness in front of them.

Why it matters

The proverb has spent sixteen hundred years insisting on the same observation: that the appraising eye, when turned on a gift, becomes ungrateful by the act of looking. What changes from version to version is whether the proverb addresses the rule (Latin), the room (Italian), the precise biting surface (Spanish), or the working economy of an actual horse-dependent peasant household (Russian).

The horse stands in the yard, mouth shut. The recipient stands in front of it. The proverb tells them, in four languages and as many centuries, not to ask the horse its age.