What did he mean when he concluded "v'Hayah Hashem Li l'Eilokim"?
Rashi: He meant that Hashem would be with him from beginning to end, in that all his children would be 'Kasher'. 1
Rashbam: That Hashem will help him in all that he does.
Ramban and Seforno: This is not part of Yakov's conditions, but part of his undertaking
As Hashem had promised when He said to Avraham (in Bereishis 17:7) "to be for you a G-d and for your children after you".
In keeping with the Gemara in Kesuvos (110b) "If someone lives in Chutz la'Aretz it is as if he does not have a G-d.
It is not clear how the verse hints that this is if he will not fulfill. (PF)
Obviously, Yakov would sacrifice only to Hashem! Perhaps it means that he will not slaughter Chulin, only Shelamim. (PF)
The Midrash (Shemos Rabah 5) says that one should say 'Lech l'Shalom', and not 'Lech b'Shalom.' Why did Yakov say 'b'Shalom'?
Imrei No'am, citing Ri: Also in a Berachah, we find "Hashem Yevarech Es Amo ba'Shalom"!
QUESTIONS ON RASHI
Rashi writes that the previous Pasuk refers to the promises that Hashem made to Yakov in his dream. What did Yakov mean when he added "v'Shavti b'Shalom El Beis Avi"?
Rashi: He meant if he would return from Lavan without sin and not learn from his ways.
Seforno: The entire phrase means that Hashem would save him illnesses, with reference to Ru'ach Ra'ah.
Ha'Emek Davar: Hashem promised to return him, but he could return stricken and afflicted, and only to the land, but not to his father's house.
Rashi writes that "v'Hayah Hashem Li l'Eilokim" means that there will not be a Pesul in his children. Where is this hinted at? Also, when is this fulfilled, at which point Yakov must make the stone a Matzevah?
Divrei David: A hint is from Hashem's promise [to Avraham] "Lihyos Lecha l'Eilokim ul'Zar'acha" (17:7).