(No, this is not one of those posts by illiterate scribes who guilt you out of addressing God in intimate terms.)
In scripture, the Father is sometimes addressed with the word “Abba” accompanying “Father“.
Though most scholars reject that “Abba” (used in Mark 14:36; Rom. 8:15; Gal. 4:6, and likely what Jesus used to pray in Matt 6:9) literally meant “Daddy” as a term of informal endearment, it is used as a term of intimacy and respect, perhaps more like “Dad”, though not necessarily non-equivalent to “Father”.
By the time Jesus walked the earth in the flesh, slaves were often forbidden to use “Abba” in a household, though they were allowed to address the head as “father” in Hebrew. Children and adults used the term. What we have here is a term denoting both respect and intimacy, reflecting that the user is a son and an heir.
Not only did Christ use this term, but so did his disciples. From this use we learn that we are not “sort of family” in the household of God, as any slave, but are adopted as children. Being his creation, we are his children by origin, but by adoption through his most beloved, we share in the heir despite our rebellion. We, like Christ, are allowed to address him with a term reserved for those children given heir to the promise.
Said Jesus, “No longer do I call you servants: for the servant knows not what his master does: but I have called you friends: for all things that I have heard of my Father, have I made known to you.” (John 15:15). Said Paul, much later, “For as many as are led by the Spirit of God, these are the sons of God. For you did not receive the spirit of bondage again to fear, but you received the Spirit of adoption by whom we cry out ‘Abba, Father.’ The Spirit himself bears witness with our spirit that we are children of God.” (Rom. 8:14-16).
Our Father wants us to draw close to him with the utmost reverence, but also with intimacy. We are his children. An we have his promise.
Everyone has at least one father-figure in their life. If they do not know their biological father, there is at least one person who is present as a male leader, authority figure, or inspiration. We learn a lot about how our own concept of God works through these figures. As a father, you will teach your son or daughter about how God is, whether you realize it or not, and your children will shape their understanding of God from all the ways they observe and interact with you.
For now, my son calls me “Daddy”. He already knows my first name. One day he will learn to call me “Dad”, and then, on certain occasions, refer to me as “Father”. I know he loves me. I know he trusts me. One day, he will learn more fully what it means to respect one you trust. I hope I can best be the model for which he can learn how his relationship to God the Father is to be. I hope he can grow to be a man and still draw to me with respect and endearment. I hope even more so that he will draw to God with even more respect and intimacy.