Torrance indicates that "Father" (a divine epithet for the Christian deity or first person of the tripersonal Godhead) is a relation rather than a description of God's essence or substance. He then continues:
"Hence Gregory Nazianzen like Athanasius insisted that they [the terms 'Father' and 'Son'] must be treated as referring imagelessly, that is in a diaphanous or 'see through' way, to the Father and the Son without the intrusion of creaturely forms or sensual images into God. Thus we may not think of God as having gender nor
think of the Father as begetting the Son or the Son as begotten after the analogy of generation or giving birth with which we are familiar among creaturely beings."
Quote taken from Thomas F. Torrance, The Christian Doctrine of God: One Being, Three Persons (Edinburgh: T & T Clark, 1996), 158.
See Nazianzen's Orationes 29.16; 31.7, 31ff.