WE ALL NEED THE HEART OF GOD...The Lord did this for Saul at the first when Samuel spoke to him...I Sam. 10: 6-10 vs 9 And it was so , that when he had turned back to go from Samuel---GOD GAVE HIM ANOTHER HEART: and all those signs came to pass that day.
vs 10 And when they came thither to the hill, behold, a company of prophets met him: and the Spirit of GOD came upon him.
God has plans and purposes for anointed LEADERS that He has put in place for A TIME of obedience.So in this story was Saul-not totally obeying ALL.
I Sam. 15: 1-3 .now therefore hearken thou unto THE VOICE of the WORDS of THE LORD. vs 2 Thus saith THE LORD of hosts, I remember that which Amalek did to Israel, he LAID WAIT for him in the way, when he came up from Egypt. vs 3 NOW Go & SMITE AMALEK, & UTTERLY destroy all that they have & spare them not; but slay both man and woman, infant,& suckling, oz & sheep, camel & ass.
I also see ,too that GOD can remove His Spirit as God did with SAUL for he kept back and did not do all! Described as I Sam.15: 19 Wherefore then didst thou not obey the voice of the Lord,but DIDST FLY UPON THE SPOIL, & didst evil in the sight of the LORD?
I Sam.15:23 for rebellion is as the sin of witchcraft,& stubbornness is as iniquity & idolatry. Because thou hast rejected the WORD OF LORD, he hath also rejected thee from being king.
-- it was time to anoint David-(THE ETERNAL KING-)
I Sam 16:1 - for I have provided me a king among his sons.
God looked on the heart of David-- chapte 16: 12 And the Lord said, Arise, anoint him: FOR THIS IS HE.vs 13 Then Samuel took the horn of oil, & anointed him in the midst of his brethern : AND THE SPIRIT OF LORD CAME upon David from that day forward. vs 14 But the SPIRIT of the LORD departed from SAUL, AND an evil spirit from the LORD troubled him.
So Saul attempted to kill David 21 times and after that many wars... to the point of Ziklag..I Sam 30 :18 And David recovered all that the Amalekites had carried away: and David rescued his two wives.THE SPOILS WHERE GIVEN TO ALL even those left at a point of not fighting in that great battle!