Exodus 32:26-28

Young's Literal Translation

²⁶ and Moses standeth in the gate of the camp, and saith, `Who [is] for Jehovah? -- unto me!' and all the sons of Levi are gathered unto him;

²⁷ and he saith to them, `Thus said Jehovah, God of Israel, Put each his sword by his thigh, pass over and turn back from gate to gate through the camp, and slay each his brother, and each his friend, and each his relation.'

²⁸ And the sons of Levi do according to the word of Moses, and there fall of the people on that day about three thousand men,