Genesis 28:21

21. 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.

John Calvin's Commentaries (1540-1563) — public domain. Text from the Calvin Translation Society English edition (1840s-50s) via the Christian Classics Ethereal Library (ccel.org). Calvin's coverage is partial (roughly two-thirds of the Bible); uncommented books and verses are honest gaps, never fabricated. The 19th-century editor's footnotes and remarks are omitted so the notes are faithfully Calvin's own voice.

21. to my father’s house in peace] It does not appear that this was literally fulfilled. Jacob, on his return, did not dwell at his father’s house. But, perhaps, “father’s house” means “the land of his fathers.” “In peace,” a common Heb. phrase, noticeable here for the rendering of LXX μετὰ σωτηρίας, “with safety.”

then shall the Lord be my God] The rendering of the margin, and the Lord will be my God, then this stone, &c., is that of the ancient versions, LXX, Lat. and Syr.: that of the text is on the whole preferable. The crowning thought is that in days to come, Jehovah, who has been the God of Abraham and Isaac, shall also be the God of Jacob. This forms the substance of Jacob’s vow; to which is added, that Bethel, as well as Beer-sheba and Hebron, shall be a place of Jehovah’s worship. Jacob’s vow, with the conditions attached to it, reflects his calculating character. But it acknowledges that Jehovah is the God who has revealed Himself to his fathers, and is distinct from mere nature-gods.

The Cambridge Bible for Schools and Colleges (gen. ed. J. J. S. Perowne; Cambridge University Press, 1878–1918) — public domain. Text from a community e-Sword module.

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 Gen 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.''

John Gill's Exposition of the Whole Bible (1746–1763) — public domain (CC PDM 1.0). Text via the HelloAO Bible API.

I will publicly own him for my God and the Saviour of men, and will establish his solemn worship, as it follows.

Matthew Poole's English Annotations on the Holy Bible (1683–1685) — public domain. Text from a community e-Sword/MySword module.

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

בשלום IN PEACE, perfectly free (שלם) from sin, not having learnt evil from Laban’s ways,

והיה ה' לי לאלהים AND IF THE LORD WILL BE MY GOD, in that His Name shall rest upon me from the beginning to the end: that no unworthy person shall be found in my descendants (Sifré, ואתחנן 31) — just as it is said (v. 15), “I will do that which I spake concerning thee”; and this promise He made to Abraham, as it is said (17:7) “To be a God unto thee and unto thy seed after thee”,

Rashi on the Tanakh — English translations: “The Judaica Press complete Tanach with Rashi, translated by A. J. Rosenberg” (CC BY 4.0); “Pentateuch with Rashi's commentary by M. Rosenbaum and A.M. Silbermann, 1929-1934” (public domain); “The Metsudah Tanach series, Lakewood, N.J” (CC BY 4.0); and “The Book of Joshua, Metsudah Publications, 1997” (CC BY 4.0). Text via Sefaria.

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: “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.]

Ramban (Nachmanides) on the Tanakh — English translation: “Commentary on the Torah by Ramban (Nachmanides). Translated and annotated by Charles B. Chavel. New York, Shilo Pub. House, 1971-1976” (CC BY 4.0). Text via Sefaria.

ושבתי בשלום, with his wife and children, for without them neither he, his father, or his mother would consider themselves at peace, seeing that he was forbidden to marry one of the Canaanite girls.

והיה ה' לי לאלוקים, this was the gist of the vow, meaning that he would concentrate on the service of the Lord and minimise any mundane activities. Furthermore, he vowed that he would build an altar on the place where he had slept on the stone which he had just anointed. יהיה בית אלוקים, he would build a Temple and altar there so that anyone worshipping the Lord could come there and pray and offer his sacrifices on that altar. It would be a Temple for the G’d in heaven only. Another way of understanding these words could be that he would instruct his children to build a Temple there in the future when they would take possession of the land of Israel. A further vow Yaakov made at this time was: וכל אשר תתן לי עשר אעשרנו לך, I will give a tithe of all the acquisitions including the cattle which You will give me. I will distribute this tithe to needy people in order to encourage them to switch to monotheism. According to Bereshit Rabbah 70,7 the vow included tithing one of his future children to G’d, i.e. appointing him as a servant of the Lord representing the other sons. [As an interesting aside, the Midrash there claims that assigning only one of 12, respectively 14 sons, if we add Ephrayim and Menashe, Yaakov did not “tithe” i.e. give 10% of his children to the Lord, he is reported as having replied that seeing that each of his four wives had one firstborn, someone whose duty it was as a firstborn to devote himself to spiritual matters without his father “donating” him to G’d for such a task, he Yaakov had done well to additionally assign Levi as a “tithe” for the remaining 10 “children.” Ed.] As to the formulation:

עשר אעשרנו לך, as a grammatically unusual formulation, this is an accepted formulation as we find it also confirmed in Deuteronomy 11,13 with the same verb, or in Deuteronomy 14,22 שמור תשמרון with a different verb. There are many similar examples of this kind of repetition for emphasis. Our sages in Ketuvot 50 use the formulation used in this verse as teaching that even if one wants to be generous in his donations to charity and holy causes, one should not give away more than 20% of one’s wealth in order not to become an object of charity himself because of carelessly squandering wealth given to one by G’d. The wordsעשר אעשרנו are understood by the Talmud there as applying to two such tithes of 10% each.

Radak on the Tanakh — English translations: “Sefaria Community Translation” (CC0 1.0 (public-domain dedication)); “Eliyahu Munk, HaChut Hameshulash” (CC BY 4.0); “Rabbi Mike Feuer, Jerusalem Anthology” (CC BY 4.0); and “R. David Kimhi on the first book of Psalms, Translated by R.G. Finch, London, 1919” (public domain). Text via Sefaria.