תהלים, פרק ק״ה, פסוק ט׳

The divine promise of the land passes from generation to generation, taking root as an eternal and unbreakable commitment. The original covenant God made with Abraham, assuring the land to his descendants, continues and grows stronger as it is handed down to Isaac [מאירי]. This agreement centers entirely on the exact promise initially established with Abraham [מצודת דוד]. Crucially, this commitment and the accompanying oath to grant the land were directed exclusively toward Isaac, bypassing Ishmael, which highlights the unique and chosen status of Jacob's descendants [אלשיך].

There is a meaningful distinction between a covenant and an oath, as an oath represents a much stronger and firmer level of commitment than a standard agreement [מלבי״ם]. The passing of this promise to Isaac gains the absolute weight of an oath through several avenues. First, the mere act of God repeating the covenant a second time with Isaac naturally elevates it to the level of a sworn oath [מלבי״ם]. Additionally, this oath traces back directly to the Binding of Isaac, where God explicitly swore that his descendants would inherit the land [רד״ק, מאירי]. Finally, when God later assured Isaac that He would fulfill the oath sworn to Abraham, it was considered as if God had made the oath directly to Isaac himself [רד״ק, אבן עזרא].