Paul likes to be a father, whether directly, For though you have countless guides in Christ, you do not have many fathers. For I became your father in Christ Jesus through the gospel.1st Corinthians 4:15. I appeal to you for my child, Onesimus, whose father I became in my imprisonment.Philemon 1:10 indirectly, It is always good to be made much of for a good purpose, and not only when I am present with you, my little children, for whom I am again in the anguish of childbirth until Christ is formed in you!Galatians 4:18, 19 or metaphorically. For you know how, like a father with his children, we exhorted…1st Thessalonians 2:11, 12
Jesus does not endorse this. In fact, Jesus endorses the opposite. And call no man your father on earth, for you have one Father, who is in heaven.Matthew 3:9 A single command from Jesus should be enough for us, but since Jesus is also the Way, we can look and see how Jesus feels about earthly fathers.
Jesus denies his earthly family. While he was still speaking to the people, behold, his mother and his brothers stood outside, asking to speak to him. But he replied to the man who told him, 'Who is my mother, and who are my brothers?' And stretching out his hand toward his disciples, he said, 'Here are my mother and my brothers! For whoever does the will of my Father in heaven is my brother and sister and mother.'Matthew 12:46-50 cf. Mark 3:31-35
Notice that last verse. "For whoever does the will of my Father in heaven is my brother and sister and mother." There is no spiritual 'father,' only brother and sister and mother. Jesus is consistent with his given command earlier.
But why would Jesus deny men the status of fatherhood in the spirit? Consider some more statements by Jesus, In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven.Matthew 5:16 So that you may be sons of your Father who is in heaven. For he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust.Matthew 5:45 Beware of practicing your righteousness before other people in order to be seen by them, for then you will have no reward from your Father who is in heaven.Matthew 6:1(See also Matthew 6:4, 6, 8, 15, 18, 7:11, 10:20, 29, Mark 11:25, Luke 6:36, 12:30, 32, John 20:17. These verses are all directed to his disciples, and he names God as their Father.)
It is because the spiritual father cannot be a human. He is God and God alone. So when Paul says that he is a father, whether directly, indirectly, or metaphorically, he is blaspheming God's position.
Let us examine one more example from Jesus's life. When Jesus was twelve years old,(Luke 2:42.) Mary and Joseph brought him and his brethren to Jerusalem. But then they left him behind by accident.(Luke 2:44.) When they found Jesus, Luke records, And when his parents saw him, they were astonished. And his mother said to him, 'Son, why have you treated us so? Behold, your father and I have been searching for you in great distress.' And he said to them, 'Why were you looking for me? Did you not know that I must be in my Father's house?' And they did not understand the saying that he spoke to them.Luke 2:48-50
Jesus implicitly denies Joseph his role as a father by saying that he "must be in my Father's house" while not standing in Joseph's house. This must have confused Joseph and Mary. Jesus was only twelve years old! Why would Jesus be so harsh to Joseph?
That answer came eighteen years later, when Jesus said, And call no man your father on earth, for you have one Father, who is in heaven.Matthew 3:9
Value of this Evidence
This is indefensible evidence against Paul apostleship. No true apostle would ever blaspheme God. Since Jesus consistently lived by this principle, even from a young age, there is no reason that any apostle should be ignorant of this principle. Paul is defenseless here.