Jesus revolutionized our understanding of God: that he is our Father and we are his children. While no Bible scholar myself, I do not remember the OT explicitly teaching the early Jews that God is their Father. They had many names for God, ones we evangelicals often quote or invoke, such as Yahweh Yireh (God Our Provider) or the like, but God our Father? Not until it abruptly appears in the Biblical narrative in the Lord’s Prayer.
This teaching of Jesus’ is so subtle I believe it’s power is often overlooked; it ought to form the bedrock of our Christian identity and inform our social relations. More to the point of this series, it has everything to do with how we ought to pray.