Ransom Captive Israel

The song "O Come, O Come, Emmanuel" asks Emmanuel, who we learned about last week, to come and ransom captive Israel. Who is captive Israel, and why does he (or they?) need to be ransomed? The song goes on to say that Israel "mourns in lonely exile" here. Why is Israel mourning, and what does all this have to do with Christmas, anyway? Pastor Luke looks at Isaiah 35:1-10 in "Ransom Captive Israel," part 2 of his 4-part series, "O Come, Emmanuel."