וְתַ֥ם לָרִ֖יק כֹּחֲכֶ֑ם וְלֹֽא־תִתֵּ֤ן אַרְצְכֶם֙ אֶת־יְבוּלָ֔הּ וְעֵ֣ץ הָאָ֔רֶץ לֹ֥א יִתֵּ֖ן פִּרְיֽוֹ׃
And your strength shall be spent in vain; for your land shall not yield her produce, neither shall the trees of the land yield their fruit.
Read halakhic rulings (Jewish law) on Leviticus 26:20: and classical halakhic sources.