The Holy One of Israel (Hebrew Qadosh Yisraʾel) is the covenant name Isaiah uses more than two dozen times, joining absolute holiness to particular relationship. He is utterly other — "high and lifted up," "Holy, holy, holy" (Isaiah 6:1-3) — and yet bound by covenant to this people, this nation, this elect bride. The name refuses the modern false choice between a transcendent God who is distant and a relational God who is soft. Israel’s LORD is the consuming fire who has also pledged Himself by oath. The Holy One sanctifies what He claims — which is why 1 Peter 1:15-16 applies the same call to the New Covenant church: "Be ye holy; for I am holy."
Webster 1828: the transcendently holy God who has covenanted with His chosen.
The title holds two truths in tension: He is the Holy One, separated from all creaturely defilement; and He is of Israel, the God who has tied Himself to a people.
Isaiah 1:4 — "They have forsaken the LORD, they have provoked the Holy One of Israel unto anger."
Isaiah 43:3 — "For I am the LORD thy God, the Holy One of Israel, thy Saviour."
Isaiah 41:14 — "I will help thee, saith the LORD, and thy redeemer, the Holy One of Israel."
Psalm 71:22 — "Unto thee will I sing with the harp, O thou Holy One of Israel."
Modernism flattens holiness into niceness and forgets the One who burns.
To call God the Holy One is to confess that He is not us writ large. He is wholly other, and to come near Him without a Mediator is to die.
Yet He is the Holy One of Israel, bound to a people. Holiness without covenant terrifies; covenant without holiness deceives.
Qadosh (holy) joined to Yisrael (Israel, prince of God).
H6918 — Qadosh — holy, set apart
H3478 — Yisrael — Israel, he who strives with God
"The Holy One of Israel is high and lifted up."
"Israel forsook the Holy One of Israel and was scattered."
"The Holy One is also our Redeemer."