Amalek was a type of the flesh and that they were the first enemy that the Israelites encountered when they fled Egypt. The battle was not won in the valley but on the mountain as Aaron and Hur held up Moses' arms (Spiritual battle). Under Saul’s rule the Lord said that Amalek must be destroyed completely, but Saul spared the best to offer to the Lord.
The Lord however makes it clear that he is not interested in anything that the flesh had to offer, not even it’s best and most noble attempts. (Obedience is better than sacrifice)
The flesh must die and only the life of the indwelling Christ and the fruits of that life are acceptable to Him.
God goes to great lengths to drive this point home.
1 Cor 1:27-29 But God hath chosen the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty; And base things of the world, and things which are despised, hath God chosen, yea, and things which are not, to bring to naught things that are: That no flesh should glory in his presence.