שׁ֗וּבוּ לַאֲשֶׁ֛ר הֶעְמִ֥יקוּ סָרָ֖ה בְּנֵ֥י יִשְׂרָאֵֽל׃
Turn ye unto Him Against whom ye have deeply rebelled, O children of Israel.
Rashi on Isaiah
Return To the One about Whom you have thought deeply how to turn away from Him, now return to Him.
Ibn Ezra on Isaiah
Turn ye unto him, etc. The prophet, addressing Israel, says: Return, ye Israelites, to God, from whom you have deeply revolted. סרה is derived from סרר to revolt. Comp. סורר rebellious (Deut. 21:18)