Albert Barnes Commentary Matthew 14:3-5

"For Herod had laid hold on John, and bound him, and put him in prison for the sake of Herodias, his brother Philip`s wife. For John said unto him, It is not lawful for thee to have her. And when he would have put him to death, he feared the multitude, because they counted him as a prophet." — Matthew 14:3-5 (ASV)

For Herod had laid hold on John. This Herodias was a granddaughter of Herod the Great. She was first married to Herod Philip, by whom she had a daughter, Salome, probably the one who danced and pleased Herod.

Josephus says that this marriage of Herod Antipas with Herodias took place while he was on a journey to Rome. He stopped at his brother's; fell in love with his wife; agreed to put away his own wife, the daughter of Aretas, king of Petraea; and Herodias agreed to leave her own husband and live with him.

They were living, therefore, in adultery; and John in faithfulness, though at the risk of his life, had reproved them for their crimes. Herod was guilty of two crimes in this act:

1. Of adultery, as she was the wife of another man;
2. Of incest, as she was a near relation, and such marriages were expressly forbidden (Leviticus 18:16).