For Jesus, the heart of God (who God is) is more important than the attributes of God (what God is).
Jesus accepts the Mosaic revelation of the name of God – Yahweh – which puts the emphasis on what God is. Yahweh is the causative form of the verb “to be” and is the first word in the complete expression of His name – Yahweh - ser-yihweh which means “He brings into being whatever comes into being.”
This remarkable revelation coincides with modern proofs of God as unique, Creator, and highest Being, but does not emphasize the heart of God. Building on this foundation, Jesus supplies the missing piece – the revelation of who God is -- by first revealing another name – Abba (Section I), and then revealing His unconditional love for us in the Parable of the Prodigal Son (Section II).
A brief explanation of each points to the heart of God. Read more by clicking the following document. Also, watch Fr. Spitzer discuss "Who is God" in the video at the bottom of the page.