When did God as "Father" become common? Jesus called him Father, but was that common?
Referring to God as “Father” took place in Old Testament times, but it was rather unusual prior to the coming of Jesus, who regularly referred to his heavenly Father, e.g., John 1:14, 18.
In the Old Testament, God is referred to as the father of the nation of Israel several times, (Deut. 32:6, Is. 63:16, Mal. 1:6). He is also referred to the father of certain people more than a dozen times, (e.g., 2 Sam. 7:14, Ps. 89:26). And at other times, the imagery of “fatherhood” is present even though the word Father is not used, (Ex. 4:22-23, Mal. 3:17).
In coming to redeem the world (see John 3:16-17), Jesus invites us into an intimate relationship with his heavenly Father in which we can call him “Abba” or “Daddy,” (e.g., Mark 14:36, Rom. 8:15, Gal. 4:6).