1741 oratorio by George Frideric Handel that includes the Hallelujah chorus (7)
I believe the answer is:
messiah
(Other definitions for messiah that I've seen before include "Hallelujah chorus work" , "His coming was prophesied in the Old Testament" , "Choral work often performed at Christmas" , "Handel's composition, sung annually by Our Lady's Choral Society" , "Expected deliverer of the Jews" .)