Jamieson, Fausset & Brown

Ye worship ye know not what--without any revealed authority, and so very much in the dark. In this sense, the Jews knew what they were about. But the most glorious thing here is the reason assigned, for salvation is of the Jews--intimating to her that Salvation was not a thing left to be reached by any one who might vaguely desire it of a God of mercy, but something that had been revealed, prepared, deposited with a particular people, and must be sought in connection with, and as issuing from them; and that people, "the Jews."