(Exodus 23:5) addresses the obligation to help an enemy's animal that is struggling under its burden: "If you see the donkey of your enemy lying under its burden." The Mekhilta parses this verse with precision, finding several limitations within its words.
"Lying" — this means an animal that has collapsed under a legitimate load. But not a habitual "lier" — an animal that routinely lies down and refuses to move. If the animal is simply obstinate rather than genuinely overburdened, the obligation does not apply.
"Under its burden" — the animal must be carrying its normal, customary load. If the owner has piled on more than the animal can reasonably carry, the obligation to help is not triggered. The owner created the problem by overloading the animal.
"And you forbear to help him" — the Mekhilta reads this phrase as establishing a conditional obligation. There are times when you must forbear (refrain from helping) and times when you must help. Not every situation triggers the obligation. The verse creates discretion.
These limitations prevent the obligation from becoming open-ended or exploitable. You must help when the need is genuine and the circumstances are reasonable. But you are not required to enable animal abuse by helping someone who habitually overloads his donkey, or to rescue an animal that simply refuses to cooperate with a normal burden.