Commentary for Genesis 28:21

ושבתי SO THAT I RETURN — even as He said (v. 15) “I will restore thee again into this land” (Genesis Rabbah 70:4),

THEN THE ETERNAL SHALL BE MY G-D. This is not a condition, as Rashi would have it. It is rather a vow, and its purport is as follows: “If I will return to my father’s house, I will worship the proper Name of the Eternal in the Chosen Land at the location of this stone which will be for me a house of G-d, and there I will set aside the tithe.” There is in this matter a secret relating to that which the Rabbis have said:⁵⁸Kethuboth 110b. “He who dwells outside the Land of Israel is like one who has no G-d.” [Thus, according to the meaning of the above quotation, the Eternal will be Jacob’s G-d only when he returns to the Land of Israel.]

ושבתי בשלום, in accordance with G’d’s promise in verse 15.