A.T. Robertson Commentary Matthew 2:16

"Then Herod, when he saw that he was mocked of the Wise-men, was exceeding wroth, and sent forth, and slew all the male children that were in Bethlehem, and in all the borders thereof, from two years old and under, according to the time which he had exactly learned of the Wise-men." — Matthew 2:16 (ASV)

Slew all the male children that were in Bethlehem (ανειλεν παντας τους παιδας τους εν Βηθλεεμ). The flight of Joseph was justified, for Herod was violently enraged (εθυμωθη λιαν) that he had been mocked by the Magi, deluded in fact (ενεπαιχθη). Vulgate illusus esset. Herod did not know, of course, how old the child was, but he took no chances and included all the little boys (τους παιδας, masculine article) in Bethlehem two years old and under, perhaps fifteen or twenty. It is no surprise that Josephus makes no note of this small item in Herod's chamber of horrors. It was another fulfilment of the prophecy in Jer 31:15. The quotation (2:18) seems to be from the Septuagint. It was originally written of the Babylonian captivity but it has a striking illustration in this case also. Macrobius (Sat. II. iv. II) notes that Augustus said that it was better to be Herod's sow (υς) than his son (υιος), for the sow had a better chance of life.