Commentaries:
That is low—not even good enough to be sold as slaves. This is how far God is willing to go to make the lessons of exile sink in. Because of sin, He has to do this as punishment. He has to separate us away from Him for a time. The purpose is to get us to repent, to bring us back to Him in the end. If this is what it takes, He is willing to do it.
It is very ironic that He says that He would rejoice in bringing Israel—or the church in type—low. This is not a fiendish type of joy in which a person gets his jollies out of making others hurt. God will rejoice because He can see the end and know that at least another step in His plan has been accomplished. He will put His whole heart into it to make sure that we come out of it as His people—in far better shape—on the other end.
Richard T. Ritenbaugh
How to Survive Exile