וְאַבְשַׁ֣י בֶּן־צְרוּיָ֗ה הִכָּ֤ה אֶת־אֱדוֹם֙ בְּגֵ֣יא הַמֶּ֔לַח שְׁמוֹנָ֥ה עָשָׂ֖ר אָֽלֶף׃
Moreover Abishai the son of Zeruiah smote of the Edomites in the Valley of Salt eighteen thousand.
Rashi
and Joab returned and smote of Edom, etc. [of] the eighteen thousand stated in Scripture (II Sam. 8:13, I Chron. 18:12), Abishai slew six thousand the first time, and Joab slew twelve thousand when he returned from battling Aram.
Rashi
When he fought Heb. בהצותו, as (Num. 26:9): “when they quarreled (בהצותם) with the Lord,” that he fought with them because they aided the Ammonites.