How does a sinner who is at enmity with God at birth become a friend of God?
First, what is the Biblical definition of friend? Friend means to have a lively, reconciled, communicative, cooperative relationship with someone else. Other words used in the Bible describing different relations are: relative, brother, enemy, sons of God.
What is distinctive about a friend? Friends are not necessarily born of the same woman or have the same family lineage. An enemy is the opposite of friend. To be a son of God is defining an eternal and divine birth status.
So to be friends would necessitate a particular type of interaction between two people thereby making them friends.
James 2:23 says, “and the Scripture was fulfilled which says, ‘And Abraham believed God, and it was reckoned to him as righteousness,’ and he was called the friend of God.”
Thus Abraham did something to bring him into a friendly relationship with God. What was it? He agreed with God on His promise. Of course we are used to the believe but what seemed to happen was a legal interaction between Abraham and God. God made Abraham a promise, Abraham agreed to the promise, he was thereby declared righteous by God leading the two into a friendly relationship.
So you would have to say that Abraham’s agreement to the terms of God’s friendship is what made them friends. In fact, Abraham’s agreement led to his salvation and thereby as a saved sinner he became a friend of God.
The same order of interaction occurs with Jesus in John 15:13-14, “Greater love has no one than this, that one lay down his life for his friends. You are My friends if you do what I command you.”
Jesus’ words have a clear stipulation to friendship: do what I tell you to do.
Of course we know that to do what He says to do implies an agreement with His offer. Again, we would say His disciples believed Him, did what He said to do and are thereby called Jesus’ friends.
It would appear clear that a sinner can become a friend of God. He does so by agreeing to the terms of salvation first, then executing his responsibilities in the terms and thereby the sinner, who is now saved and a son of God is also a friend of God.