זְכָר־אֵ֣לֶּה יַעֲקֹ֔ב וְיִשְׂרָאֵ֖ל כִּ֣י עַבְדִּי־אָ֑תָּה יְצַרְתִּ֤יךָ עֶֽבֶד־לִי֙ אַ֔תָּה יִשְׂרָאֵ֖ל לֹ֥א תִנָּשֵֽׁנִי׃
Remember these things, O Jacob, And Israel, for thou art My servant; I have formed thee, thou art Mine own servant; O Israel, thou shouldest not forget Me.
Read halakhic rulings (Jewish law) on Isaiah 44:21 from the Mishneh Torah and classical halakhic sources, free online.