The Holy Spirit, since He sanctifies creatures, is neither a creature nor subject to change. He is always good, since He is given by the Father and the Son; neither is He to be numbered among such things as are said to fail. He must be acknowledged as the source of goodness. The Spirit of God’s mouth, the amender of evils, and Himself good. Lastly, as He is said in Scripture to be good, and is joined to the Father and the Son in baptism, He cannot possibly be denied to be good. He is not, however, said to progress, but to be made perfect in goodness, which distinguishes Him from all creatures.
The Holy Spirit is not, then, of the substance of things corporeal, for He sheds incorporeal grace on corporeal things; nor, again, is He of the substance of invisible creatures, for they receive His sanctification, and through Him are superior to the other works of the universe. Whether you speak of Angels, or Dominions, or Powers, every creature waits for the grace of the Holy Spirit. For as we are children through the Spirit, because God sent the Spirit of His Son into our hearts crying, Abba, Father; so that you are now not a servant but a son; Galatians 4:6-7 in like manner, also, every creature is waiting for the revelation of the sons of God, whom in truth the grace of the Holy Spirit made sons of God. Therefore, also, every creature itself shall be changed by the revelation of the grace of the Spirit, and shall be delivered from the bondage of corruption into the liberty of the glory of the children of God.
Every creature, then, is subject to change, not only such as has been changed by some sin or condition of the outward elements, but also such as can be liable to corruption by a fault of nature, though by careful discipline it be not yet so; for, as we have shown in a former treatise, the nature of Angels evidently can be changed. It is certainly fitting to judge that such as is the nature of one, such also is that of others. The nature of the rest, then, is capable of change, but the discipline is better.
Every creature, therefore, is capable of change, but the Holy Spirit is good and not capable of change, nor can He be changed by any fault,
Saint Ambrose On the Holy Spirit (Book I), Chapter 5
— Kendall Harmon (@KendallHarmon6) December 7, 2017