The Mekhilta offers an alternate reading of the verse "You will bring them and You will plant them." The key word is "plant." God does not merely promise to place Israel in the land. He promises to plant them — and this is a planting that will never be uprooted.
Jeremiah spells out the terms of this divine commitment (Jeremiah 24:6): "And I shall plant and not uproot. And I shall build them and not destroy them." The language is absolute. No uprooting, no destruction. The planting is permanent. Amos delivers the same promise with even greater emphasis (Amos 9:15): "And I will plant them on their land and they will not be uprooted again."
The word "again" in Amos is critical. It acknowledges that uprooting has happened before — exile, displacement, loss of the land. But the final planting, the one God promises through the prophets, will be different. It will be irreversible. The roots will go so deep that no empire, no conquest, no catastrophe will be able to tear Israel from its soil.
The midrash (rabbinic interpretive commentary) reads the Song at the Sea as looking far beyond the immediate journey to Canaan. The "planting" described here is eschatological — it points to the ultimate restoration, when God's promise of permanence will finally be fulfilled and the cycles of exile and return will come to an end.