Deuteronomy 29:18

29:18 Beware that the heart of no man, woman, clan, or tribe among you turns away from the Lord our God today to pursue and serve the gods of those nations; beware that there is among you no root producing poisonous and bitter fruit. ¹ 

Deuteronomy 29:25

29:25 Then people will say, “Because they abandoned the covenant of the Lord, the God of their ancestors, which he made with them when he brought them out of the land of Egypt.

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¹ tn Heb “yielding fruit poisonous and wormwood.” The Hebrew noun לַעֲנָה (la’anah) literally means “wormwood” (so KJV, ASV, NAB, NASB), but is used figuratively for anything extremely bitter, thus here “fruit poisonous and bitter.”