אֲשֶׁ֣ר עַל־כֵּ֭ן סָ֣רוּ מֵֽאַחֲרָ֑יו וְכָל־דְּ֝רָכָ֗יו לֹ֣א הִשְׂכִּֽילוּ׃
דערפֿאַר װאָס זײ האָבן זיך אָפּגעקערט פֿון אים, און אױף אַלע זײַנע װעגן ניט געאַכט.
Rashi
Because they turned away from following Him Heb. אשר על-כן as in (Num. 10:31), “because (על- כן) you knew our camping in the desert.” [This is] like: because (מפני אשר) they turned away from following Him, and they brought before Him and upon Him the cry of the poor.