The gifts given to the priests and Levites are not merely economic privileges; they form a system that demands strict spiritual and legal care. The Levites are instructed on how to separate a portion from the tithes they themselves receive from the Israelites, with a strong emphasis on the severe consequences of treating these holy gifts with disrespect.
The primary approach among commentators is that the instructions are phrased negatively to teach a positive obligation. The Torah is not simply promising that proper separation will save a person from sin, which is self-evident. Instead, it serves as a warning that if the Levites fail to separate the portion properly, they will bear guilt, and if they profane what is holy, they will die [רש״י, שפתי חכמים, מזרחי]. The indirect phrasing regarding the penalty of death indicates that this is a punishment delivered directly by Heaven, rather than by a human court [גור אריה, רלב״ג].
When separating the portion for the priests, there is an obligation to give the finest and most beautiful part of the crop [ביאור שטיינזלץ, מלבי״ם]. Anyone who separates inferior produce instead of the best commits a sin, though after the fact, the separation remains valid and is considered a proper tithe [תורה תמימה, רש״ר הירש].
The warning against profaning the holy things of the Israelites operates on several levels. Fundamentally, it prohibits eating the produce before the required portion has been properly separated [רלב״ג, אבן עזרא, ביאור יש״ר], as well as strictly forbidding the consumption of holy items in a state of impurity [רשב״ם, מלבי״ם]. Until the portion is separated, the Levites must not treat the produce as ordinary food, nor should they take its holiness lightly simply because they themselves are holy servants [העמק דבר]. Furthermore, it is forbidden to casually snack on a tithe that was taken early while the crop was still in the stalks. Once it is designated as a tithe, it becomes holy, and eating it before it is properly prepared is considered a profanation [תורה תמימה]. However, once the portion has been correctly separated, the remainder of the crop becomes completely ordinary, and the danger of profanation passes [חזקוני, ביאור שטיינזלץ]. Commentators also note that while Levites are permitted to eat their tithes anywhere, they are warned not to intentionally defile the crop, as the Israelites have already sanctified it with a blessing [שפתי כהן].
Beyond the legal restrictions regarding impurity and untithed produce, another form of profanation involves the honor of God's servants. Priests and Levites are warned against working as simple laborers in threshing floors or slaughterhouses just to win the favor of the owners and receive tithes as wages. Such behavior reduces heavenly gifts to economic favors dependent on the goodwill of the giver, which degrades their spiritual status and profanes the holiness of the gifts [תורה תמימה, צפנת פענח, רש״ר הירש].
On a moral and conceptual level, this warning also serves as a lesson for the leaders of the nation. They are cautioned never to speak ill of the Israelites or profane their honor. God desires the well-being of the Israelites, and leaders who spoke harshly against the nation, such as Moses and Elijah, were ultimately punished for doing so [שפתי כהן].