Deuteronomy 32:20

מה אחריתם [I WILL SEE] WHAT THEIR END SHALL BE — i.e. what will come upon them in the end. כי דור תהפכת המה FOR THEY ARE A GENERATION OF PERVERSITY - i.e. they change (הפך) My goodwill into anger. לא אמן בם means, My training is not evident in them, for I showed them the good way and they have deviated from it. אמן is of the same meaning as in (Esther 2:7) “And he brought up (אמן) Hadassah”. Nouriture in old French — Another explanation of אמן: it has the same meaning as אמונה, faithfulness, as the Targum takes it (“in whom there is no faithfulness”). At Sinai they said, “We will do and we will hearken” and after a very short time they broke their promise and made the golden calf (Sifrei Devarim 320:6).

And he said, I will hide my face from them, I will see what their end shall be: for they are a very perverse generation, children in whom is no faith.

וַיֹּ֗אמֶר אַסְתִּ֤ירָה פָנַי֙ מֵהֶ֔ם אֶרְאֶ֖ה מָ֣ה אַחֲרִיתָ֑ם        כִּ֣י ד֤וֹר תַּהְפֻּכֹת֙ הֵ֔מָּה בָּנִ֖ים לֹא־אֵמֻ֥ן בָּֽם׃