Luther

As regards His Godhead, He [the Holy Ghost] is of indivisible divine essence with the Father and the Son; but to us He is called a Comforter, and a comforter is one who makes a sad heart glad and joyful towards God and tells you to be of good cheer for your sins are forgiven, death is slain, heaven is open, and God smiles on you. Whoever could grasp this definition rightly would have already won the victory and would not find or see anything but sheer comfort and joy in heaven and on earth.—Exposition, John xiv