וַיִּנָּ֤גְפוּ שָׁם֙ עַ֣ם יִשְׂרָאֵ֔ל לִפְנֵ֖י עַבְדֵ֣י דָוִ֑ד וַתְּהִי־שָׁ֞ם הַמַּגֵּפָ֧ה גְדוֹלָ֛ה בַּיּ֥וֹם הַה֖וּא עֶשְׂרִ֥ים אָֽלֶף׃
And the people of Israel were smitten there before the servants of David, and there was a great slaughter there that day of twenty thousand men.
Read midrashic interpretation of II Samuel 18:7: and classical rabbinic exegesis.