Then said Saul, I have sinned: return, my son David; for I will no more do you harm, because my life was precious in your eyes this day: behold, I have played the fool, and have erred exceedingly.
"Return, my son David"  (1 Samuel 26:21).  If one wonders why David did not trust Saul here, the answer lies in his hypocritical use of the words "my son," not only here, but in  1 Samuel 26:25.  They were proof enough that Saul was lying in his teeth, and David instantly knew it.