A promise of peace does not always erase deep distrust. After David swears to fulfill Saul's request, the two leaders immediately part ways. Saul heads back to his home, while David and his followers retreat to the safety of the stronghold.
Despite the agreement they just reached, David and his men deliberately choose not to travel back with the king. Commentators explain that David knows very well that he cannot rely on Saul's words. Fully aware that the king's promises offer no real guarantee of safety, David decides to keep his distance rather than return with him.