The Gospel of Matthew narrates that after the magi failed to return to him as instructed, Herod the Great, ruler of Judea under Roman authority, ordered the killing of all male children in and around Bethlehem two years old and under, calculating the age from the time the star had reportedly appeared to the magi. Matthew presents the episode as fulfilling a prophetic text from the book of Jeremiah describing Rachel weeping for her children, and narrates that Joseph, warned in a dream, had already taken Mary and the infant Jesus and fled to Egypt before the massacre occurred, sparing the family the fate the other children of the town suffered.
No other Gospel, and no source outside the New Testament, mentions this event, a silence that stands out against what is otherwise known about Herod's reign from the first century Jewish historian Josephus, who documents Herod's considerable cruelty, including the execution of several of his own family members, in substantial detail without recording any massacre at Bethlehem.
The feast commemorating the episode, the Holy Innocents, is kept within the Christmas season in the Western liturgical calendar, on 28 December, honoring the children as the earliest martyrs associated with Christ's birth even though their historicity as a specific, dated event is not independently attested.