In the year that king Uzziah died I saw also the Lord sitting upon a throne, high and lifted up, and his train filled the temple. Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly. And one cried unto another, and said, Holy, holy, holy is the LORD or hosts: the whole earth is full of his glory. –Isaiah 6: 1-3
Isaiah’s vision in Isaiah Chapter 6, and Holy, Holy, Holy always go together, in my mind.
This is the King’s College Choir, singing the hymn.