Straightway - Immediately, or as soon as possible.
Took counsel - Laid a plan. Consulted with them. Literally, “made a consultation.”
The Harridans - See the notes at Matthew 22:16.
How they might destroy him - They hated him, he was so holy; because he reproved them; because he laid open their hypocrisy; and because he won the hearts of the people and lessened their influence. They therefore determined to remove him, if possible, and thus avoid his reproofs. Sinners would often rather put to death the man that reproves them than forsake their sins. The Pharisees had rather commit any crime, even to the murder of the Messiah, than forsake the sins for which he rebuked them.