Albert Barnes Commentary Judges 4:21

"Then Jael Heber`s wife took a tent-pin, and took a hammer in her hand, and went softly unto him, and smote the pin into his temples, and it pierced through into the ground; for he was in a deep sleep; so he swooned and died." — Judges 4:21 (ASV)

If we can overlook the treachery and violence which belonged to the morals of the age and country, and bear in mind Jael’s ardent sympathies with the oppressed people of God, her faith in the right of Israel to possess the land in which they were then slaves, her zeal for the glory of Yahweh as against the gods of Canaan, and the heroic courage and firmness with which she executed her deadly purpose, we will be ready to accord her the praise which is her due. See Judges 3:30 note.