16 Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven. Matthew 5:16 (NASB)
15 For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, “Abba! Father!” Romans 8:15 (NASB)
As Christians we must understand that we are indeed adopted children of God. We were of our father the devil (John 8:44; 1 John 3:8-10). Under him we were indeed, slaves, slaves to sin, under a sentence of death, already dead in trespasses and sins (Ephesians 2:1-3). But we have been adopted into the family of God. We are members of a new family, all the old debts are paid, and we are new people with a new Father.
In the New Testament there are two Greek words translated as Father. The first is πατήρ (patēr), from which are derived English words such as paternity and paternal. In Greek philosophy it referred to the patriarchal head of the family. Most notably however, the Jews of the Old Testament saw five basic principle concerning God’s Fatherhood.