Ambrose of Milan

Oneness in Godhead the Law hath proved, which speaks of one God, as also the Apostle, by saying of Christ; "In Whom dwelleth all the fulness of the Godhead bodily." For if, as the Apostle saith, all the fulness of the Godhead, bodily, is in Christ, then must the Father and the Son be confessed to be of one Godhead; or if it is desired to sunder the Godhead of the Son from the Godhead of the Father, whilst the Son possesses all the fulness of the Godhead bodily, what is supposed to be further reserved, seeing that nothing remains over and above the fulness of perfection? Therefore the Godhead is one.