The social and spiritual fabric of ancient Israel relied heavily on the support of its dedicated spiritual class. The Levites lived scattered throughout the various cities of the nation [רש״ר הירש]. Instead of working the land, they served as spiritual guides and devoted scholars, deeply immersed in the study of Torah [העמק דבר, שפתי כהן]. Because they were dedicated to this communal role, they did not receive an agricultural inheritance of their own and lacked the means to support themselves independently [תורה תמימה, ביאור שטיינזלץ].
To sustain them, the Israelites are commanded to provide for the Levite living in their own local community [ביאור שטיינזלץ]. The tithe must be given directly to this local Levite, rather than searching for another one elsewhere or forcing him to travel to Jerusalem to collect his portion [אבן עזרא, חזקוני, שפתי כהן].
The primary approach among commentators is that the strict warning to consistently support the Levite refers specifically to the obligation of giving him the First Tithe [רש״י, אבן עזרא, מזרחי, גור אריה, בכור שור]. Because the preceding instructions dealt with the Second Tithe, which is eaten in Jerusalem, a person might mistakenly conclude that fulfilling that duty is sufficient. Therefore, it is stressed that giving the Second Tithe does not exempt anyone from providing the First Tithe to the Levite [אבן עזרא, חזקוני, ברכת אשר].
Beyond formal tithing, another approach expands this duty to include the overall well-being and joy of the Levite. This involves inviting him to share in holiday celebrations, hosting him at the family table, and ensuring he enjoys comfort and abundance. Since his constant engagement in Torah study leaves him no time to pursue extra comforts, the community must step in [רשב״ם, העמק דבר, בכור שור, ביאור יש״ר]. Even if a person does not have a First Tithe to give, the obligation to care for the Levite remains active. He must still be supported through other means, such as different tithes, portions of sacrificial meat, or communal charity funds [תורה תמימה, רש״ר הירש].
The underlying reason for supporting the Levite also establishes a fundamental rule regarding the laws of tithing. The Levite is granted the tithe specifically because he lacks a portion of land. Consequently, any produce in which the Levite already shares an equal right with the rest of the public is entirely exempt from tithing. This includes ownerless produce and the agricultural gifts designated for the poor, such as gleanings, forgotten sheaves, and the corners of the field. Since the Levite has the same right to take from these as anyone else, the standard obligation to separate tithes from them does not apply [רש״י, מזרחי, שפתי חכמים].