What was the relationship between Herod the Great and Jesus?
When Jesus was born, Herod was king of Judea. He learned from the magi that a king had been born, and he searched for the child to kill him. Matthew 2:1-3, 13
What the Bible says
Matthew 2:3
And king Herod hearing this, was troubled, and all Jerusalem with him.
Matthew 2:13
And after they were departed, behold an angel of the Lord appeared in sleep to Joseph, saying: Arise, and take the child and his mother, and fly into Egypt: and be there until I shall tell thee. For it will come to pass that Herod will seek the child to destroy him.
Douay-Rheims Bible (Challoner revision), public domain.
What the Church teaches
For the Catechism, the massacre of the Holy Innocents shows the opposition of darkness to the light.
Catechism 530 · Catechism of the Catholic Church
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Meet Herod the Great and Jesus.