Numbers 16:46-48

46And Moses said to Aaron, "Take your censer, and put fire on it from off the altar and lay incense on it and carry it quickly to the congregation and make atonement for them, for wrath has gone out from the Lord; the plague has begun."

47So Aaron took it as Moses said and ran into the midst of the assembly. And behold, the plague had already begun among the people. And he put on the incense and made atonement for the people.

48And he stood between the dead and the living, and the plague was stopped.