Take them alive. — Perhaps they made some show of resistance. Jehu slew them because of their connection with the doomed house of Ahab. Keil thinks he dreaded their conspiring with the partisans of the fallen dynasty in Samaria.
Slew them at the pit of the shearing house. — Literally, slaughtered them into the cistern of Betheked. Either they cut their throats over the cistern, or threw the corpses into it.
Two and forty. — Curiously parallel with 2 Kings 2:24; and perhaps a definite for an indefinite number.