When the Lord has thoroughly proved him, and finds that the man is determined to serve Him at all hazards, then the man will find his calling and his election made sure, then it will be his privilege to receive the other Comforter, which the Lord hath promised the Saints, as is recorded in the testimony of St. John, in the 14th chapter, from the 12th to the 27th verses….
Thus does He make Him equal to Him for by proceeding from Himself He became His first-begotten Son, because begotten before all things" (Κατά Πραξέα, 7) "Ο Τερτυλλιανός επιβεβαιώνει το ομοούσιο του Υιού και του Πνεύματος με τον Πατέρα" (Φλορόφσκυ Γεώργιος, Οι Βυζαντινοί Πατέρες του 5ου αιώνα, Πουρναράς, Θεσσαλονίκη 1992, σελ. 202).