David spared the life of Saul but took away his

This event is recorded in 1 Samuel 26:7-12. David and Abishai crept into Saul's camp at night while Saul and his soldiers were in a deep sleep sent by the Lord. They found Saul sleeping with his spear stuck in the ground at his head and a jar of water beside him.

Abishai wanted to kill Saul, but David refused, saying he would not raise his hand against the Lord's anointed. Instead, David took Saul's spear and jar of water (1 Samuel 26:12) and withdrew to a safe distance. From a hilltop, David called out to Abner, Saul's commander, displaying the spear and water jar as proof that he had been close enough to kill Saul but had chosen to spare his life.

This act of taking the spear and water jar served two purposes: it proved David's presence in the camp, and it demonstrated his mercy and respect for Saul's position as king. The other options - bow and arrow, iron shield - are not mentioned in this narrative. The items specifically taken were the spear and the jar of water.