a joy that would last

And the ransomed of the LORD shall return and come to Zion with singing; everlasting joy shall be upon their heads; they shall obtain gladness and joy, and sorrow and sighing shall flee away. 

Isaiah 51:11

God promised His people that joy would fill them again. It would come after tragedy, devastation, and judgment; but it would eventually come to them. The survivors of the Babylonian captivity would return to Zion with joy. They would ascend the Temple Mount singing the praises of their Redeemer. They would be a ransomed people.

A joy that would last would mark their praise. God's deliverance would be full and free. They would feel it and it would fill them. They would sing the praises of a saving God. It would be a true worship from the heart.

The singing would replace their sorrow and sighing. God would give them a joyful worship that would supplant their pain. They would live in joy and gladness again. The hope of this experience would have to carry them through exile.