On The Holy Trinity by St. Augustine
Chapter 15.--Whether the Holy Spirit Was a Gift Before as Well as After He Was Given.
16. But it is asked further, whether, as the Son, by being born, has not only this, that He is the Son, but that He is absolutely; and so also the Holy Spirit, by being given, has not only this, that He is given, but that He is absolutely -- whether therefore He was, before He was given, but was not yet a gift; or whether, for the very reason that God was about to give Him, He was already a gift also before He was given. But if He does not proceed unless when He is given, and assuredly could not proceed before there was one to whom He might be given; how, in that case, was He [absolutely] in His very substance, if He is not unless because He is given? just as the Son, by being born, not only has this, that He is a Son, which is said relatively, but His very substance absolutely, so that He is. Does the Holy Spirit proceed always, and proceed not in time, but from eternity, but because He so proceeded that He was capable of being given, was already a gift even before there was one to whom He might be given? For there is a difference in meaning between a gift and a thing that has been given. For a gift may exist even before it is given; but it cannot be called a thing that has been given unless it has been given.