God is the Father of His People

J. Scott Lidgett wrote a book called The Fatherhood of God. He attempted to trace how the doctrine of God's relationship to man developed through the Old Testament. Lidgett argued that the people originally talked about the god of their fathers, not God the Father. They stressed God's sovereignty and kingship, not His fatherhood. Lidgett argued that the idea of God's fatherhood actually developed only very late in Israel's history, though it became a central theme in the New Testament.

In the nations around Israel, it was very common to call God "father". The nations around Israel believed that gods gave birth to other gods just as people gave birth to other people. So most gods were either the father or mother of other gods. Now, rulers in the Ancient Near East claimed a special relationship with the gods. For example, a Pharaoh in Egypt claimed to be the great manifestation of the god Horas, son of Osiris. So Pharaoh claimed to be both god and son of god. The rulers in the Tigris Euphrates Valley were lest inclined to call themselves gods, however, these rulers did call themselves the sons of god. There's even one interesting text where all the people in the land are called collectively "sons of god". The father rule of the Mesopotamian gods seems to grow from the fact that all things were created by the gods.

Old Testament passages where God is called a Father.
In Isaiah 45:11, 12 and Isaiah 64:8 God was their Father because He created them. In Isaiah 43:6, 7 God's sons are those that are called by His name. Very few things in the Old Testament were called by His name. Being called by God's name was a very special honor which was normally reserved for things that He uniquely claimed. God's sons were those whom God Himself called by His own name. In Isaiah 63:8-16 Israel was His sons due to the fact that He redeemed them. Sonship here is based on God reaching out in mercy and redeeming His people. Isaiah 63:9 says that Israel was God's sons because He had placed on them His special Father-like love. Time and again God declared to Israel and His Father-like compassion, and He called them to respond. In Psalm 103:13 Israel knew God as Father in a continual give-and-take relationship with Him. Like any Father who would require certain things of His sons, God expected certain actions from Israel. This list could go on and on.