1 Samuel 26:21
Then said Saul, I have sinned: return, my son David: for I will no more do thee harm, because my soul was precious in thine eyes this day: behold, I have played the fool, and have erred exceedingly. Then said Saul, I have sinned: return, my son David: for I will no more do thee harm, because my soul was precious in thine eyes this day: behold, I have played the fool, and have erred exceedingly.
The verse belongs to the time after Saul slew the Lord's priests, when Abiathar son of Ahimelech escaped and fled after David, and David told him to abide with him and fear not, for he that sought David's life sought his life, but with David he would be in safeguard. It is Saul's answer after David spared his life a second time by taking his spear and water jar while he slept and then calling to him from a hilltop. David had asked why Saul kept pursuing him and what wrong he had done, and Saul answered by admitting his sin and folly.
In the verse Saul admits he has sinned, declares he has played the fool and erred exceedingly, and promises to do David no more harm because his life was precious in David's eyes that day. This confession is more humble than his first one, because Saul was astonished and subdued by David's kindness in sparing his life. Yet Saul's promise did not change him for long, and David knew it would not last, so he refused Saul's call to return and would not put himself back in Saul's power.