Saul said to Samuel, I have sinned; for I have transgressed the commandment of Yahweh, and your words, because I feared the people, and obeyed their voice.
After Samuel's refusal to grant Saul's request here; and as Samuel turned to go away, Saul was frantic and determined, if possible, to reverse the situation, by grabbing hold of Samuel's garment to detain him.  The garment was torn.