Matthew 14:3

For Herod had laid hold on John. This arrest of John the Baptist had taken place a year previous, shortly before our Lord's second visit to Galilee (Mt 4:12 Mr 1:14), the events of which are given by John (Joh 4:43-54). The prison was the castle of Machaerus.

See PNT Mt 11:2.

For the Herodias' sake. Antipas had been, while at Rome, the guest of his brother Herod Philip. Here he became entangled by the snares of Herodias, his brother Philip's wife; and he repaid the hospitality he had received by carrying her off. He had himself long been married to the daughter of Aretas, king of Arabia. This Herodias was the granddaughter of "Herod the King", and, hence, the niece of both her lawful husband and of Herod Antipas, who now had her.
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