פּירוש אויף בראשית 28:22

והאבן הזאת THEN THIS STONE — This is how you should explain the ו of והאבן: if He will do these things mentioned in Genesis 28:15 as He promised, then I, also, will do this:

והאבן הזאת literally: “and this stone,” but the meaning must be: “I will offer sacrifices and separate tithes on this stone (altar).” The letter ו at the beginning of the word: והאבן, appears superfluous.

'וכל אשר תתן לי וגו, “and all that You will give to me, etc.;” Yaakov promised to tithe all the money (material goods) that he would acquire with the help of G–d. (B’reshit Rabbah, 70,7) A heretic once asked Rabbi Yoshua son of Levi, where the Torah reported that Yaakov kept this promise. He was answered that Yaakov declared this tithe “sacred,” i.e. he gave it to the treasury of religious institutions. Thereupon the heretic wanted to know what this tithe consisted as precisely seeing that Yaakov was not a wealthy man. He was told that Yaakov made all his newly born animals pass under a gate, and every tenth animal he declared as holy, i.e. not to be used for secular needs. In the Talmud this procedure is called: מעשר בהמה, “tithe from livestock.” [Since Yaakov did not plant crops, not owning any arable land in the land of Canaan (except one small field near Sh’chem from which he moved away before it could produce a crop), he could not tithe his crops. The version in my edition of B’reshit Rabbah is slightly different but the point is made that Yaakov certainly did not default on his vow. Ed.]

והאבן הזאת אשר שמתי מצבה THEN THIS STONE WHICH I HAVE SET UP FOR A PILLAR etc. — Explain it as the Targum translates it: “I shall serve the Lord upon it” This, indeed, he did on his return from Padan-aram, when God said to him, (Genesis 35:1) “Arise, go up to Bethel”. What is stated there? “And Jacob set up a pillar … and he poured out a drink-offering thereon” (Genesis 35:14).