The Mekhilta presents a striking conflict between two obligations. A Kohen — a priest — encounters a lost or struggling animal in a cemetery. Jewish law prohibits a Kohen from entering a cemetery and becoming ritually impure through contact with the dead. But the Torah also commands returning lost property and helping animals in distress.

Which obligation takes priority? The Mekhilta rules: the Kohen does not become impure for the animal. He stays out of the cemetery. The prohibition against priestly impurity overrides the obligation to return lost property.

The Mekhilta then considers a more difficult scenario. What if the Kohen's father says to him: "Go into the cemetery and make yourself impure"? A child is obligated to honor and obey his parents. The command to honor parents is a positive commandment. The prohibition against priestly impurity is a negative commandment. In general, a positive commandment overrides a negative one.

Even so, the Kohen may not obey. The Torah says "and you forbear to help him" — there are times when forbearance is correct. This is one of those times. The Torah's inclusion of a "forbearance" option specifically addresses situations where other commandments conflict with the helping obligation. The Kohen forbears because his priestly status takes precedence. Not even filial obedience can compel him to violate it.