The Mekhilta DeRabbi Yishmael records a teaching by Rabbi Yishmael on the laws governing an unpaid bailee who is entrusted with livestock. The verse states: "If a man give to his neighbor an ass or an ox or a lamb" (Exodus 22:9), and Rabbi Yishmael derives from it the same critical distinction he applied to the earlier verse about money and vessels.
The ruling is precise: for a person to become legally bound as a guardian of another's animals, the deposit must be made explicitly. The depositor must say something equivalent to "Here, watch this for me," making it unambiguous that he is placing his animal in the other person's care with the expectation of responsible guardianship. These clear words create the legal relationship of bailment.
But if the depositor merely says "Keep an eye on it," without formally handing over the animal, the neighbor is not liable if the animal is lost, stolen, injured, or dies. The casual request, however reasonable it might sound in everyday conversation, does not rise to the level of a legal deposit. No obligation attaches to vague language.
Rabbi Yishmael's insistence on explicit language reflects a core principle in Jewish property law: legal obligations must be created through clear, unambiguous acts. This is not mere formalism. Animals, unlike money or vessels, can wander off, get sick, be attacked by predators, or cause damage to others. The stakes of guardianship are high. The Mekhilta's ruling ensures that no one becomes an involuntary bailee, burdened with responsibility they never clearly accepted. If you want someone to guard your ox, you must say so plainly. If you merely hint, the law does not hold them accountable. Clarity protects both parties.