"I will be who I will be" But who will He be? Exodus 3:14

I am that I am exodus 3:14

He existed before anything other than himself came into being. The Father is singular while being many, for he is the first one and the one who is only himself. Yet he is not like a solitary individual. Otherwise, how could he be a father? For whenever there is a "father," the name "son" follows. But the single one, who alone is the Father, is like a root, with tree, branches and fruit. (The Tripartite Tractate)

God told Israel that His Name was YAHWEH, meaning "I am that I am" or, more correctly translated, 'I will be who I will be' (Ex.3:13-15). This name was then slightly extended: "God said moreover (i.e. in addition) unto Moses, Thus shalt thou say unto the children of Israel, Yahweh God of your fathers, the God of Abraham, the God of Isaac and the God of Jacob...this is My name for ever, and my memorial to all generations" (Ex.3:15).

Thus God's full name is therefore Yahweh God or "Yahweh Elohim".

The Old Testament was written mostly in Hebrew, and our English translation inevitably misses out a lot of detail when it comes to translating the Hebrew words for 'God'. One of the common Hebrew words translated 'God' is 'Elohim', meaning 'mighty ones'. God's "memorial", the Name by which He wants us to remember Him, is therefore

YAHWEH ELOHIM

meaning

HE WHO WILL BE REVEALED IN A GROUP OF MIGHTY ONES.

It is therefore God's purpose to reveal His character and His essential being in a large group of people. By obedience to His word we can develop some of God's characteristics in ourselves now, so that in a very limited sense God is revealing Himself in the true believers in this life. But God's Name is a prophecy of the time to come when the earth will be filled with people who are like Him, both in character and by nature (cp. 2 Pet.1:4 by which have been given to us exceedingly great and precious promises, that through these you may be partakers of the divine nature, having escaped the corruption that is in the world through lust). 

If we wish to be associated with the purpose of God and to become like God to die no more, living for ever in complete moral perfection, then we must associate ourselves with His Name. The way to do this is to be baptized into the Name - i.e. Yahweh Elohim (Matt.28:19). This also makes us the descendants ("seed") of Abraham (Gal.3:27-29) who were promised the eternal inheritance of the earth (Gen.17:8; Rom.4:13) - the group of 'mighty ones' ('Elohim') in whom the prophecy of God's Name will be fulfilled.