Ellicott's Commentary On The Whole Bible
Psalms 98 - Introduction
XCVIII.
This psalm plainly belongs to that cycle of literature produced by the joy of the Restoration, and is in fact little more than a compilation from Isaiah 40:26, and from other psalms, especially Psalms 96. The psalm is irregular in form.
Title. — This is the only hymn of the whole collection with the bare inscription “a psalm.”