This is not the Christmas carol – this is a song with a text by Cyril Alington set to GELOBT SEI GOTT (aka VULPIUS). It is suitable for Easter and Christ the King. It was added by OCP for 2026.
The text is available at Hope Publishing, who also have the sheet music. OCP have added a Trinitarian fifth verse and so claim some copyright and you can get their version there.
I found an old backing: