4. Mose (Bamidbar) 32:14

לספות is similar in meaning to the verbs in (Isaiah 29:1): “add (ספו) year to year”; ( 7:21): “add (ספו) your burnt-offerings” — an expression denoting adding (The translation is: to add even more to the Lord’s fierce anger against Israel).

וְהִנֵּ֣ה קַמְתֶּ֗ם תַּ֚חַת אֲבֹ֣תֵיכֶ֔ם תַּרְבּ֖וּת אֲנָשִׁ֣ים חַטָּאִ֑ים לִסְפּ֣וֹת ע֗וֹד עַ֛ל חֲר֥וֹן אַף־יְהֹוָ֖ה אֶל־יִשְׂרָאֵֽל׃

And, behold, you are risen up in place of your fathers, a brood of sinful men, to augment yet the fierce anger of the Lord towards Yisra᾽el.