In Matthew 6:9 Jesus tells His disciples how to pray. He begins His instruction by teaching His disciples to address God as “Our Father in heaven.” To the Jewish ear this might have sounded like an awkward way to speak to God. Throughout the Old Testament and Jewish tradition God is addressed in a variety of ways, but rarely is He called “Father.” Jesus all but introduces this terminology to Jewish culture.
One of the rare occasions where we see God explicitly called “Father” is in Isaiah 9:6, where we find the prophet speaking not of God the Father, but rather God the Son.
It is only as followers of the Son that we can approach our Father in heaven.