The first occasion on which the terms of the relationship were made plain was when God showed himself to Abraham as El Shaddai (God Almighty, God All-Sufficient) and formally gave him the covenant promise,

"to be your God and the God of your descendants after you."  Genesis 17:1-7.

All Christians inherit this promise through faith in Christ, as Paul argues in Galatians 3:15-29.  What does it mean?  It is in truth a pantechnicon promise:  it contains everything.   

"This is the first and fundamental promise, " declared Sibbes, the Puritan;  "Indeed, it is the life and soul of all the promises" (Works IV,8). 

Brooks, another Puritan, opens it up as follows:

"That is as if he said, You shall have as true an interest in all my attributes for your good, as they are mine for my own glory....My grace, saith God, shall be yours to pardon you, and my power shall be yours to protect you, and my wisdom shall be yours to direct you, and my goodness shall be yours to relieve you, and my mercy shall be yours to supply you, and my glory shall be yours to crown you." 

This is a comprehensive promise, for God to be our God:  it includes all, said Luther.  (Works Y, 308)

This is true love to any one when we do the best for him we can.  That is what God does for those He loves - the best He can;  and the measure of the best that God can do is omnipotence!  Thus faith in Christ introduces us into a relationship big with incalculable blessing, both now and for eternity.