דברי הימים א, פרק כ״א, פסוק ו׳

A royal command is usually carried out without question, but when an order threatens the safety of the nation, a loyal commander might find ways to resist. Joab harbored a deep opposition to King David's directive to conduct a national census. The king's order was entirely unacceptable and deeply distasteful to him [מצודת דוד, ביאור שטיינזלץ]. Knowing in advance that counting the people would bring guilt and a devastating plague upon the nation, Joab actively sought to sabotage the mission. He evaded completing the task in full, hoping to protect at least a portion of the population from the impending disaster [רש״י, ביאור שטיינזלץ].

To achieve this, Joab deliberately excluded the tribes of Levi and Benjamin from the census. He prepared strong justifications ahead of time, anticipating the king's anger over his failure to follow orders. For the tribe of Levi, Joab planned to rely on historical precedent, arguing that they were never counted alongside the rest of the Israelites even during the time of Moses [רש״י, מצודת דוד]. Furthermore, this excuse aligned with the practical reality on the ground. The Levites were scattered among the other tribes, lacking a defined geographic territory or a standard military formation [ביאור שטיינזלץ].

The decision to skip the tribe of Benjamin stemmed from a desire to protect a fragile community. The primary approach among commentators is that Benjamin was a small tribe that had previously suffered massive casualties during the civil war of the concubine at Gibeah. They had not yet fully recovered from this tragic loss. Joab reasoned that their numbers were already dangerously low, and if a plague were to strike as a consequence of the census, the tribe could be completely wiped out. Because of Joab's intentional omissions, the final population figure he presented to the king was not based on a precise count of these two tribes. Instead, any numbers representing them were merely rough estimates factored into the overall total [מצודת דוד].