To sheathe the sword/ to return the sword to its sheath
He returned the sword to its sheath. In the question: He ceased fighting (the meaning of the sword sheath is discussed).
("And the Lord said to his angel, and he returned his sword to its sheath" - Deuteronomy 1:27, the Lord to his angel to stop the plague, and so: "The sword shall return to its sheath, and the sea of peace shall return to its strength as at the beginning, lest I should require you to trouble yourself yet again, to waste time for nothing" - Shu't Sha'ilat Ya'abetz Helek, Part 2, Simeon Koch)
Translation
Expression (Hebrew)
הֵשִׁיב חֶרֶב לִנְדָנָהּ
Definition (Hebrew)
הֶחֱזִיר אֶת הַחֶרֶב לְנַרְתִּיקָהּ. בְּהַשְׁאָלָה: הִפְסִיק לְהִלָּחֵם (נָדָן מַשְׁמָע נַרְתִּיק הַחֶרֶב).
("וַיֹּאמֶר ה' לַמַּלְאָךְ וַיָּשֶׁב חַרְבּוֹ אֶל נְדָנָהּ"- דִּבְרֵי הַיָּמִים א כא כז, ה' לַמַּלְאָךְ לְהַפְסָקַת הַמַּגֵּפָה, וְכֵן:"תָּשׁוּב הַחֶרֶב לִנְדָנָהּ וַיֵּשֶׁב יַם הַשָּׁלוֹם לְאֵיתָנוֹ כְּבָרִאשׁוֹנָה בְּלִי שֶׁאֶצְטָרֵךְ לִטְרֹחַ עוֹד בְּכָךְ לְאַבֵּד הַזְּמַן בְּחִנָּם"- שׁוּ"ת שְׁאִילַת יַעְבֵּץ חֵלֶק ב סִימָן כֹּה)