What is the difference between Jesus being begotten of the Father and the Holy Spirit proceeding from the Father?
St. Gregory the Theologian said: “You ask, what is the procession of the Holy Spirit? Do you tell me first what is the unbegotteness of the Father, and I will then explain to you the physiology of the generation of the Son, and the procession of the Spirit, and we shall both of us be stricken with madness for prying into the mystery of God.”
John of Damascus said, “We have learned that there is a difference between generation [begetting] and procession, but the nature of the difference we in no wise understand.”
For more information please visit this link: http://suscopts.org/messages/lectures/pneumlecture3.pdf