Hallelujah is a compound of two Hebrew words: hallelu, praise ye (a command addressed to more than one person), and Yah, the shortened form of the divine name Yahweh, the LORD. So hallelujah is not merely a happy exclamation but an imperative — a summons to praise God together. Wherever the King James Version says praise ye the LORD, the Hebrew behind it is hallelujah.
It gathers at the Bible's climaxes of joy. The Psalter ends with five hallelujah psalms in a row, building to let every thing that hath breath praise the LORD. And in Revelation, the word bursts out in Greek form — Alleluia — as heaven celebrates the reign of God. It is the one Hebrew word the whole world has learned to sing.
Hallelujah in Scripture
Let every thing that hath breath praise the LORD. Praise ye the LORD.