דברי הימים א, פרק כ״ט, פסוק כ״ז

The summary of King David’s reign reflects a long journey of growth and establishment, marked by significant highs and lows. Taking the throne as a relatively young man around the age of thirty [ביאור שטיינזלץ], David led the nation for forty years. His leadership unfolded in two primary phases: an initial seven-year period in Hebron, followed by a thirty-three-year era in Jerusalem.

Historically, his time in Hebron actually lasted seven years and six months. However, the final tally leaves out this extra half-year to arrive at an even forty years. One way to understand this omission is simply that the count rounds to the nearest year, choosing not to focus on individual months. Another perspective connects this missing time to the rebellion led by Absalom. For six months, David was forced to flee from his own son, a time of exile that cannot truly be counted as a period of proper royal rule. Therefore, those six months spent on the run are subtracted from the extra six months he ruled in Hebron, perfectly balancing the total to exactly forty years of active kingship [מצודת דוד].