במדבר, פרק ג׳, פסוק מ״ב

The census of the firstborn Israelites conducted by Moses highlights the exact precision required to fulfill God's instructions. This event represents a deep integration of the written law and the oral tradition. Although Moses was given explicit written commands, his actions were also guided by an unwritten tradition passed directly to him from God [העמק דבר]. This additional layer of instruction was essential for clarifying exactly who qualified to be included in the count.

The instructions dictated that the census applied exclusively to those whose firstborn status belonged entirely to the Israelites. If the mandate had broadly included anyone with an Israelite father, it would have counted individuals born to an Israelite father and a mother from the tribe of Levi. However, the precise parameters of the count excluded such individuals. According to the law, the holy status of a firstborn depends entirely on the mother. Therefore, a firstborn son born to a Levite mother is naturally exempt from the commandment of redemption. Guided by the oral tradition, Moses knew not to count these specific children. Because they were already exempt from redemption, they did not need a member of the Levite tribe to replace their holy status [העמק דבר].