Then shall the Lord be my God. In these words Jacob binds himself never to apostatize from the pure worship of the One God; for there is no doubt that he here comprises the sum of piety. But he may seem to promise what far exceeds his strength; for newness of life, spiritual righteousness, integrity of heart, and a holy regulation of the whole life, were not in his own power. I answer, when holy men vow those things which God requires of them, and which are due from them as acts of piety; they, at the same time, embrace what God promises concerning the remission of sins by the help of his Holy Spirit. Hence it follows that they ascribe nothing to their own strength; and also, that whatever falls short of entire perfection does not vitiate their worship, because God, mercifully and with paternal indulgence, pardons them.

So that I come again to my father's house in peace,.... In safety from Esau, and all other enemies, as God promised him he should:
then the Lord shall be my God; not as if he should not be his God if he did not do all this for him; which would savour not only of a mercenary spirit, but of great impiety; neither of which were to be found in Jacob: but the meaning is, that he should not only continue to own him as his God, and to worship him, but having fresh obligations upon him, should be stirred up more eagerly and devoutly to serve him in a very singular way and manner, and particularly by doing what is expressed in Genesis 28:22. Some think he has respect to the Messiah, owning him to be the true God with the Father and the blessed Spirit, who had appeared to Abraham, and was the fear of Isaac, and whom Jacob now owned as his God: this receives some confirmation from the Targum of Jonathan, which begins the paragraph thus,"if the Word of the Lord will be my help, &c. then the Lord shall be my God.''