Charles Ellicott Commentary 1 Samuel 20:25

"And the king sat upon his seat, as at other times, even upon the seat by the wall; and Jonathan stood up, and Abner sat by Saul`s side: but David`s place was empty." — 1 Samuel 20:25 (ASV)

David’s place was empty.—All took place as the two friends had calculated. Saul’s seat was by the wall—then, as now, in the East the highest place of honor was opposite the door. The exact meaning of the phrase “and Jonathan arose” has been disputed. The Septuagint translates this differently, based on another text: “He (Saul) went before Jonathan.” Keil, however, refers to this as “the senseless rendering of the Greek Version.” The interpretation of this difficult passage offered by Abarbanel and Rashi seems, on the whole, to be the best.

According to this view, Jonathan had already seated himself after Saul. When David’s absence was observed, “he (Jonathan) arose and seated Abner at Saul’s side.” This means Abner was placed in the seat David had left vacant, so that the seat next to Saul would not be empty, while Jonathan himself had taken the seat on Saul's other side.

This rendering considers vayêshev as causative, a verb in the Hiphil conjugation, written defectively, as in 2 Chronicles 10:2; Lange supports this interpretation and also quotes Kitto, who suggests an explanation for why Saul expected David’s presence at the new moon feast at all.

Kitto’s explanation is that David, after the strange events at Naioth by Ramah, would have supposed (as the king thought) that Saul’s feelings toward him had completely changed. David would have assumed that now, after the ecstatic state Saul had fallen into, Saul would once more be friendly with him as before.