וַיַּכֵּ֥ם דָּוִ֛ד מֵהַנֶּ֥שֶׁף וְעַד־הָעֶ֖רֶב לְמָֽחֳרָתָ֑ם וְלֹֽא־נִמְלַ֤ט מֵהֶם֙ אִ֔ישׁ כִּי֩ אִם־אַרְבַּ֨ע מֵא֧וֹת אִֽישׁ־נַ֛עַר אֲשֶׁר־רָכְב֥וּ עַל־הַגְּמַלִּ֖ים וַיָּנֻֽסוּ׃
And David smote them from the twilight even unto the evening of the next day; and there escaped not a man of them, save four hundred young men, who rode upon camels and fled.
Rashi on I Samuel
Of the next day. The Amaleikites are accustomed to being defeated on the second day [of battle], as it is stated, "tomorrow I will stand…"3Shemos 17:9. Therefore, it states, "on the(ir) next day."