The term holy one
is a name for God (see Isaiah 1:4; Isaiah 5:19, Isaiah 5:24; Isaiah 6:3; Isaiah 40:25) that indicates his separateness or otherness, as one very different from any creature. His uniqueness is found particularly in his transcendence, his divinity, seen in the glory that belongs to him.
7 “And to the angel of the church in Philadelphia write: ‘The words of the holy one, the true one, who has the key of David, who opens and no one will shut, who shuts and no one opens.