Charles Ellicott Commentary Lamentations 3:63

"Behold thou their sitting down, and their rising up; I am their song." — Lamentations 3:63 (ASV)

Their sitting down, and their rising up ... —The two words, as in Deuteronomy 6:7, Deuteronomy 11:19, and Psalm 139:2, include the whole daily and hourly conduct of those spoken of.

I am their music. —The noun, though not identical, is cognate with that of Psalm 69:12, of which the complaint is, as it were, an echo.