Here you go, follow this through from the start
Exodus 17:14 And the LORD said unto Moses, Write this or a memorial in a book, and rehearse [it] in the ears of Joshua: for I will utterly put out the remembrance of Amalek from under heaven.
Exodus 17:16 For he said, Because the LORD hath sworn that the LORD will have war with Amalek from generation to generation.
Duet 25:17Remember what Amalek did unto thee by the way, when ye were come forth out of Egypt;
Duet 25:18 How he met thee by the way, and smote the hindmost of thee, even all that were feeble behind thee, when thou wast faint and weary; and he feared not God.
Duet 25:19 Therefore it shall be, when the LORD thy God hath given thee rest from all thine enemies round about, in the land which the LORD thy God giveth thee for an inheritance to possess it, that thou shalt blot out the remembrance of Amalek from under heaven; thou shalt not forget it.
1Sam 15:2Thus saith the LORD of hosts, I remember that which Amalek did to Israel, how he laid wait for him in the way, when he came up from Egypt.
2Sam 15:3 Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass.
1Sam 28:18 Because thou obeyedst not the voice of the LORD, nor executedst his fierce wrath upon Amalek, therefore hath the LORD done this thing unto thee this day.
Whereas Jeus said, ye have heard hate your enemies, now I say unto love your enmies. There they were to execute his wrath, whereas now we execute His mercy.