פּירוש אויף בראשית 15:15

ואתה תבוא BUT THOU SHALT COME etc. Thou shalt not behold all this.

AND THOU SHALT COME TO THY FATHERS IN PEACE. And thou shalt not behold at this. Thus the language of Rashi.
This is not correct according to Rashi’s own interpretation, namely, that the decree, thy seed shall be a stranger in a land not their own,³²³Above, Verse 13. took effect as soon as Abraham had a child. Thus, soon after Isaac was born it states, And Abraham sojourned (‘vayagar’) in the land of the Philistines;³²⁴Further, 21:34. The word vayagar has the same root letters as geir (stranger), thus suggesting that Abraham lived as a “stranger” in a land which was not his own. And Isaac sojourned in Gerar.³²⁵Ibid., 26:6. The verse however states, vayeshev (and he “dwelled”), and not vayagar. In Rashi a different verse is quoted: Sojourn (‘gur’) in this land. (Ibid., Verse 3.) Now gur has the same root as vayagar. (See preceding note.) Now if so, Abraham was also included in the decree! But the meaning of the verse, And thou shalt come to thy fathers in peace, is that “no punishment will come to you from Me even though I decree on your children punishments of servitude and affliction.”

ואתה תבא אל אבותיך בשלום, you will die in peace, i.e. you will not witness in your lifetime any of the upsetting developments of which I have spoken to you. As far as the word אבותיך is concerned, this is a common expression used by most people as a metaphor making death sound less negative. Expressions such as ויאסף אל עמיו, "he was gathered in to his people" in Genesis 49,33, or והאסף אל עמיך, "be gathered in to your people" in Deuteronomy 32,50 all express similar sentiments. Some commentators (quoted by Rashi) claim that the wording proves that Terach, Avraham's father had discarded idolatry and accepted monotheism prior to his own death. This is problematic, seeing that we find in Chronicles II 34,28 that kind Yoshiyahu is told by G'd הנני אוסיפך אל אבותיך, and we know that his father Amon died as an unrepentant sinner. תקבר בשיבה טובה, you will see sons and grandsons before you die.

אל אבותיך UNTO THY FATHERS — His father was an idolator and yet it (the text) announced to him that he (Abraham) would go to him! But this teaches you that Terah repented of his evil ways (Genesis Rabbah 30:4).