This can be stated in active form. Alternate translation: "the sacrifices that they offered to the dead" (See: [[rc://en/ta/man/jit/figs-activepassive]])
"The dead" refers to the idols and gods that the Israelites were worshiping. Alternate translation: "to gods who are dead" or "to lifeless gods" (See: [[rc://en/ta/man/jit/figs-nominaladj]])