Albert Barnes Commentary Matthew 2:20

"Arise and take the young child and his mother, and go into the land of Israel: for they are dead that sought the young child`s life." — Matthew 2:20 (ASV)

They are dead which sought, etc. This either refers to Herod alone, as is not uncommon, using the plural number for the singular; or it may refer to Herod and his son Antipater. He was of the same cruel disposition as his father, and was put to death by his father about five days before his own death.