An early non-Christian reference to the crucifixion of Jesus is likely to be Mara Bar-Serapion's letter to his son, written sometime after AD 73 but before the 3rd century AD. The letter includes no Christian themes and the author is presumed to be a pagan. The letter refers to the retributions that followed the unjust treatment of three wise men: Socrates, Pythagoras, and "the wise king" of the Jews. Some scholars see little doubt that the reference to the execution of the "king of the Jews" is about the crucifixion of Jesus, while others place less value in the letter, given the possible ambiguity in the reference.
When did Socrates write a letter to his son about the crucifixion?