Ellicott's Commentary On The Whole Bible
Psalms 100 - Introduction
C.
This liturgic psalm, which as a hymn is so universally known and loved, is composed of four verses of triplets. Even when performed in the Temple, amid the exclusive notes of Judaism, its opening words must have inspired something of that catholic sentiment which pervades a congregation when singing what we know as the “Old Hundredth.”
Title. — Of praise. — Better, for thanks, or, possibly for the thankoffering, i.e., especially adapted for that particular ceremony. At all events it is a liturgical direction. LXX., “for (Vulg., in) confession.”