I was reading בחינת דת, a work of Hashkafa by Elias ben Moise del Medigo and in it he references* an argument between Rashi and the Ra'avid regarding the meaning of HaMelech HaKadosh. The context is apparently that some use this as evidence that one (or both?) of them had access to Kabbalah, and he is dismissive of the claim - however he neither describes the nature of the claim nor refutes it.
What is the argument and where is each found in the original works of Rashi and the Ra'avid respectively?
Brownie points: How does that argument relate to Kabbalah?
*I have seen a claim that the commentary on the bottom of this print was written by a Maskil.