Then God turned, and gave them up to worship the host of heaven; as it is written in the book of the prophets, O ye house of Israel, have ye offered to me slain beasts and sacrifices by the space of forty years in the wilderness?
Then God turned - changing His method with them: as they had turned from Him, so now He turned from them,
And gave them up - judicially abandoned them (see the note at Romans 1:24)
To worship the host of heaven - to star-worship, a fact which, though not expressly mentioned in the Pentateuch, is implied in those forms of idolatry to which we know that they were addicted, such as the worship of Moloch, presently to be mentioned.
As it is written in the book of the prophets - the twelve minor prophets, regarded as one book (the words are from Amos 5:25-27) "O ye house of Israel, have ye offered to me slain beasts and sacrifices by the space of forty years in the wilderness?"