According to Luke, why was John the Baptist imprisioned by Herod?

ANSWER

rebuking Herod over marying his brothers wife

Luke 3 :

(19) But when John rebuked Herod the tetrarch because of his marriage to Herodias, his brother’s wife, and all the other evil things he had done, (20) Herod added this to them all: He locked John up in prison.
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