55. But no one will doubt that the Spirit is one, although very many have doubted whether God be one. For many heretics have said that the God of the Old Testament is one, and the God of the New Testament is another. But as the Father is one Who both spake of old, as we read, to the fathers by the prophets, and to us in the last days by His Son; Heb. i. 1, 2. “and as the Son is one, Who according to the tenour of the Old Testament was offended by Adam, Gen. iii. 17. seen by Abraham, Gen. xviii. 22, 23. worshipped by Jacob; Gen. xxviii. 17. so, too, the Holy Spirit is one, who energized in the prophets, 2 Pet. i. 21. was breathed upon the apostles, S. John xx. 22. and was joined to the Father and the Son in the sacrament of baptism. S. Matt. xxviii. 19. For David says of Him: “And take not Thy Holy Spirit from me.” Ps. li. [l.] 11. And in another place he said of Him: “Whither shall I go from Thy Spirit?” Ps. cxxxix. [cxxxviii.] 7.