Judges 9:43
And he took the people, and divided them into three companies, and laid wait in the field, and looked, and, behold, the people were come forth out of the city; and he rose up against them, and smote them. And he took the people, and divided them into three companies, and laid wait in the field, and looked, and, behold, the people were come forth out of the city; and he rose up against them, and smote them.
The verse records Abimelech's ambush of the people as they came out of the city, dividing his men into three companies and lying in wait in the field before rising against them and striking them down. This attack was part of his utter destruction of Shechem, in which about a thousand people in the tower of Shechem were destroyed. Shechem itself was the very ancient stopping-point of Jacob on his return from Padan-aram to Canaan.
Abimelech was the son of Gideon's maid, who caused his brothers, Gideon's sons, to be killed or slain so that he could become ruler, thus gaining the throne by treachery. The people of Shechem had chosen him as ruler despite that fratricide. The attack came after three years of wicked, tyrannical rule, when the city rebelled against him. During that rule he governed with demoralizing cruelty, putting to death everyone who opposed his will.
The verse falls within the larger record of Judges 3-17, which depicts Israel's backsliding from God and the resulting suffering, oppression, and captivity, as well as returns to God, forgiveness, and deliverance. The lying in wait and smiting of the people coming out of the city was the fulfillment of Jotham's words in discord, strife, and hatred between Abimelech and his subjects. It was the beginning of retribution upon both the king and the Shechemites who had made him king.
Jotham's parable condemns the folly of choosing Abimelech. It teaches that those who do the most valuable work for God do not seek rule over fellow workers, so that ambition to be exalted over others shows a lack of qualification for leadership. Abimelech was permitted to execute God's vengeance upon Israel by slaying the inhabitants, reducing the city to ashes, and sowing the ground with salt as a token of perpetual desolation. That end teaches that sin will never go unpunished and warns of the danger of entering the path of disobedience.