NOTE: When this post was written, it incorrectly stated that Arius was a bishop. He was a presbyter.
The Saint Nicholas Center recounts the tale:
In AD 325 Emperor Constantine convened the Council of Nicaea, the very first ecumenical council. More than 300 bishops came from all over the Christian world to debate the nature of the Holy Trinity. It was one of the early church's most intense theological questions. Arius, from Egypt, was teaching that Jesus the Son was not equal to God the Father. Arius forcefully argued his position at length. The bishops listened respectfully.
As Arius vigorously continued, Nicholas became more and more agitated. Finally, he could no longer bear what he believed was essential being attacked. The outraged Nicholas got up, crossed the room, and slapped Arius across the face! The bishops were shocked. It was unbelievable that a bishop would lose control and be so hotheaded in such a solemn assembly. They brought Nicholas to Constantine. Constantine said even though it was illegal for anyone to strike another in his presence, in this case, the bishops themselves must determine the punishment.
The bishops stripped Nicholas of his bishop's garments, chained him, and threw him into jail. That would keep Nicholas away from the meeting. When the Council ended a final decision would be made about his future.
Nicholas was ashamed and prayed for forgiveness, though he did not waver in his belief. During the night, Jesus and Mary his Mother, appeared, asking, "Why are you in jail?" "Because of my love for you," Nicholas replied. Jesus then gave the Book of the Gospels to Nicholas. Mary gave him an omophorion, so Nicholas would again be dressed as a bishop. Now at peace, Nicholas studied the Scriptures for the rest of the night.
When the jailer came in the morning, he found the chains loose on the floor and Nicholas dressed in bishop's robes, quietly reading the Scriptures. When Constantine was told of this, the emperor asked that Nicholas be freed. Nicholas was then fully reinstated as the Bishop of Myra.
The Council of Nicaea agreed with Nicholas' views, deciding the question against Arius. The work of the Council produced the Nicene Creed which to this day many Christians repeat weekly when they stand to say what they believe.
But did it actually happen? Did the patron saint of children give Arius more than coal in his stocking?
Well, the story is most likely apocryphal. First, most scholars doubt that Nicholas was present at the First Council of Nicaea. The only mention of Nicholas' attendance was offered by Theodore the Lector two hundred years after the Council in his Historia Tripartita, but the best lists of council attendees do not include him.
But even if Nicholas was there, fisticuffs did not take place. The first mention of the incident comes one thousand years after the council in the fourteenth century AD by Bishop Petrus de Natalibus. He writes,
It happened that saint Nicholas, now an old man, was present at the Council of Nicaea, and out of jealousy of faith struck a certain Arian in the jaw, on account of which it is recorded that he was deprived of his mitre and pallium; on account of which he is often depicted without a mitre.
Notice Petrus doesn't mention that he punched Arius specifically, but a "certain Arian."
The truth of the matter is that we know little of the real St. Nicholas. It is difficult to extrapolate fact from legend. So, while it could be possible, though not likely that Nicholas was present at Nicaea, he certainly didn't punch or slap Arius or anyone else during the deliberations. It wasn't acceptable then, nor is it proper now to slap a fellow cleric over a disagreement, albeit an important one. While it may be a disappointment to some contemporary theologians, such drama will always be out of place during theological deliberations.
So, keep the coffee coming.
For Further Reading in Addition to the Links Above.
"Let's Stop Celebrating St. Nicholas Punching Arius," https://www.ncregister.com/blog/let-s-stop-celebrating-st-nicholas-punching-arius.
"Did St. Nicholas punch Arius at the Council of Nicaea?" https://christianity.stackexchange.com/questions/54016/did-st-nicholas-punch-arius-at-the-council-of-nicaea.