Deuteronomy 25:17-19

17"Remember what Amalek did to you on the way as you came out of Egypt,

18how he attacked you on the way when you were faint and weary, and cut off your tail, those who were lagging behind you, and he did not fear God.

19Therefore when the Lord your God has given you rest from all your enemies around you, in the land that the Lord your God is giving you for an inheritance to possess, you shall blot out the memory of Amalek from under heaven; you shall not forget.