Judges 9:18

And ye are risen up against my father’s house this day, and have slain his sons, threescore and ten persons, upon one stone, and have made Abimelech, the son of his maidservant, king over the men of Shechem, because he is your brother;)

Cross-references

Judges 9:5 recounts Abimelech's murder of the seventy sons, the very event Jotham accuses them of in 9:18.

Judges 9:6 describes the coronation of Abimelech by Shechem, which Jotham references as their making him king.

Judges 9:14 is part of Jotham's parable where trees ask the bramble to reign; 9:18 applies that to making Abimelech king.

Judges 8:31 introduces Abimelech as Gideon's son by a concubine, the 'son of his female servant' referenced in 9:18.

Judges 8:35 notes Israel's ingratitude to Gideon's house; 9:18 gives the specific betrayal of killing his sons.