וַיֹּ֕אמֶר אָנֹכִ֥י הָאֵ֖ל אֱלֹהֵ֣י אָבִ֑יךָ אַל־תִּירָא֙ מֵרְדָ֣ה מִצְרַ֔יְמָה כִּֽי־לְג֥וֹי גָּד֖וֹל אֲשִֽׂימְךָ֥ שָֽׁם׃
האָט ער געזאָגט: איך בין גאָט, דער גאָט פֿון דײַן פֿאָטער, זאָלסט ניט מוֹרא האָבן אַראָפּצונידערן קײן מִצרַיִם, װאָרום פֿאַר אַ גרױס פאָלק װעל איך דיך דאָרטן מאַכן.
Rashi
אל תירא מרדה מצרימה FEAR NOT TO GO DOWN TO EGYPT — God said this to him because he was grieved that he was compelled to leave the Land of Israel (Pirkei DeRabbi Eliezer 39).
Chizkuni
אלוקי אביך, “the G-d of your father.” G-d appeared to Yaakov in the same mode as Yaakov had addressed him, i.e. this is why He describes Himself as “the G-d of your father “
Sforno
I am … God of your father. I am the God who told your father not to go to Egypt (26:2), yet I am telling you to go. There I will make you into a great nation. Whereas if you remain here your offspring will intermarry with the Canaanites. This will not happen in Egypt because the populace will not even eat with the Hebrews; see 43:32