Judges 4:21

Then Jael Heber's wife took a nail of the tent, and took an hammer in her hand, and went softly unto him, and smote the nail into his temples, and fastened it into the ground: for he was fast asleep and weary. So he died.

Then Jael ... took a nail of the tent - a wooden or iron pin-most probably one of the pins, about a foot long and sharp at one end, with which the tent ropes are fastened to the ground. Escape was almost impossible for Sisera. But the taking of his life by the hand of Jael was deliberate murder. It was a direct violation of all the notions of honour and friendship that are usually held sacred among pastoral people, and for which it is impossible to conceive a woman in Jael's circumstances to have had any motive, except that of gaining favour with the victors. Though predicted by Deborah, the act was the result of divine foreknowledge, not of divine appointment or sanction; and though it is raised in the song contained in the following chapter, the eulogy must be considered as pronounced, not on the moral character of the woman and her deed, but on the public benefits which, in the overruling providence of God, would flow from it.