Leviticus 18:16 forbids marrying a brother's wife — the very law John cites to rebuke Herod.

Leviticus 20:21 declares taking a brother's wife as impurity, underlying John's condemnation of Herod's marriage.

Matthew 14:3 confirms John's arrest was directly because of his rebuke about Herodias — the same event from another gospel.

Matthew 14:4 records John's identical rebuke to Herod — a parallel account of the same confrontation.

Luke 3:19 records the same event: Herod was reproved by John for Herodias. This is a synoptic parallel confirming the account.