As far as we can reach, He Who Is, and God, are the special names of His Essence; and of these especially He Who Is, not only because when He spoke to Moses in the mount, and Moses asked what His Name was, this was what He called Himself, bidding him say to the people 'I Am has sent me' (Ex. 3:14), but also because we find that this Name is the more strictly appropriate.
Gregory of NazianzusGod always was, and always is, and always will be. Or rather, God always Is. For Was and Will be are fragments of our time, and of changeable nature, but He is Eternal Being. And this is the Name that He gives to Himself when giving the Oracle to Moses in the Mount. For in Himself He sums up and contains all Being, having neither beginning in the past nor end in the future; like some great Sea of Being, limitless and unbounded, transcending all conception of time and nature, only adumbrated [intimated] by the mind, and that very dimly and scantily.
Gregory of NazianzusMay God preserve me from being rich while they are indigent, from enjoying robust health if I do not try to cure their diseases, from eating good food, clothing myself well and resting in my home if I do not share with them a piece of my bread and give them, in the measure of my abilities, part of my clothes and if I do not welcome them into my home
Gregory of NazianzusOur starting-point must be the fact that God cannot be named... no mind has yet contained or language embraced God's substance in its fullness. No, we use facts connected with Him to outline qualities that correspond with Him, collecting a faint and feeble mental image from various quarters. Our noblest theologian is not one who has discovered the whole - our earthly shackles do not permit us the whole - but one whose mental image is by comparison fuller, who has gathered in his mind a richer picture, outline, or whatever we call it, of the truth.
Gregory of Nazianzus