וַיִּבְחַר־ל֨וֹ שָׁא֜וּל שְׁלֹ֣שֶׁת אֲלָפִים֮ מִיִּשְׂרָאֵל֒ וַיִּהְי֨וּ עִם־שָׁא֜וּל אַלְפַּ֗יִם בְּמִכְמָשׂ֙ וּבְהַ֣ר בֵּֽית־אֵ֔ל וְאֶ֗לֶף הָיוּ֙ עִם־י֣וֹנָתָ֔ן בְּגִבְעַ֖ת בִּנְיָמִ֑ין וְיֶ֣תֶר הָעָ֔ם שִׁלַּ֖ח אִ֥ישׁ לְאֹהָלָֽיו׃
And Saul chose him three thousand men of Israel; whereof two thousand were with Saul in Michmas and in the mount of Beth-el, and a thousand were with Jonathan in Gibeath-benjamin; and the rest of the people he sent every man to his tent.
Metzudat David on I Samuel
in order to be ready to serve in times of need