Tafsiran Mazmur 9:8: Rashi & Radak

But the Lord shall sit forever, etc. The Name shall be complete and the throne shall be complete, as it is written כסאו, but before it is erased, it is written (in Exod. 17:16): “For a hand is on the throne (כס) of the Eternal (י-ה).” The throne is lacking [i.e., it is spelled defectively] and the Name is divided [i.e., the final two letters of the Tetragrammaton are missing].

But the Lord sitteth enthroned for ever: – These every one may perish; but the Lord sitteth enthroned for ever, and judges these every one. And this is what he means when he says:

He hath prepared His throne for judgment, – as it says (Ps. 102:27), “they shall perish, but Thou remainest.” And the significance of sitteth enthroned (יֵשֵׁב) is that of enduring and stability; and so (in the passage) “The Lord sat enthroned at the flood” (Ps. 29:10).