עַל־כֵּ֣ן לֹא־נִ֭ירָא בְּהָמִ֣יר אָ֑רֶץ וּבְמ֥וֹט הָ֝רִ֗ים בְּלֵ֣ב יַמִּֽים׃
Therefore will we not fear, though the earth do change, And though the mountains be moved into the heart of the seas;
Rashi on Psalms
when the earth changes in the future, on the day concerning which Scripture states (Isa. 51: 6): “and the earth shall rot away like a garment.” The sons of Korah saw the miracle that was performed for them, that all those around them were swallowed up while they [the sons of Korah] stood in the air and said to Israel, through the holy spirit, that a similar miracle would be performed for them in the future.