Deuteronomy 28:40

ישל means, it (the olivetree) shall drop its fruits. It is similar in meaning to the verb in (Deuteronomy 19:5), "And the iron falleth off (ונשל).

זֵיתִ֛ים יִהְי֥וּ לְךָ֖ בְּכׇל־גְּבוּלֶ֑ךָ וְשֶׁ֙מֶן֙ לֹ֣א תָס֔וּךְ כִּ֥י יִשַּׁ֖ל זֵיתֶֽךָ׃

Thou shalt have olive trees throughout all thy borders, but thou shalt not anoint thyself with the oil; for thy olive shall cast its fruit.