Sforno on Genesis 28:15/ספורנו על בראשית כ״ח:ט״ו

1כי לא אעזבך, when I said that after the exile you will expand in all directions of the globe, know no boundaries, this is possible only because even during the long years of exile I did not abandon you, as stated explicitly in Leviticus 26,44 לא מאסתים ולא געלתים, “I will not have rejected them, nor will I have abhorred them.”

2עד אשר אם עשיתי, as long as I have not carried out what I have said to you now. (i.e. the part commencing with ופרצת). There are occasions when the word עד is used in the sense of בעוד, such as Song of Songs 1,12 עד שהמלך במסבו, ”while the king was on his couch.” Or, Proverbs 8,26 עד לא עשה ארץ וחוצות, “while G’d had not yet made earth or even clumps of dust.” However, once G’d would have performed this great salvation, not only would He continue to treat His people with loving kindness by not abandoning them, but He would add a new dimension to it by walking among them, as promised in Leviticus 26,12 והתהלכתי בתוככם, “I will be walking amongst you (constantly).”