וַיֹּ֨אמֶר יְהוָ֜ה אֶל־מֹשֶׁ֗ה כְּתֹ֨ב זֹ֤את זִכָּרוֹן֙ בַּסֵּ֔פֶר וְשִׂ֖ים בְּאָזְנֵ֣י יְהוֹשֻׁ֑עַ כִּֽי־מָחֹ֤ה אֶמְחֶה֙ אֶת־זֵ֣כֶר עֲמָלֵ֔ק מִתַּ֖חַת הַשָּׁמָֽיִם׃
Yang Mahakekal berfirman kepada Musa, “Tuliskanlah hal ini sebagai peringatan di dalam kitab, dan tanamkanlah ke telinga Yosua, bahwa Aku pasti akan menghapuskan ingatan akan Amalek dari kolong langit.”
Rashi
כתב זאת זכרון WRITE THIS FOR A MEMORIAL, that Amalek came to wage war against Israel before any other nation.
Chizkuni
כתוב, “record in writing!” but not only orally; if this piece of history would be handed down from father to son only orally, it would be exposed to becoming forgotten in the course of time.[When G-d eventually commanded King Shaul to carry out the commandment to wipe out Amalek, and that nation had not had any contact with the Jewish people for 200 years, none of the Israelites would have understood why they had to commit this kind of genocide. Ed.] The written Torah itself had foretold in Deuteronomy25,19, that this commandment would be carried out only after the Jewish people faced no more enemies all around it.
Da'at Zekenim
כי מחה אמחה, “for I will completely wipe out, etc.” the repetition of the verb is to tell us that both in this world and in the world to come there will eventually remain no descendants of Amalek.