Musannaf Ibn Abi Shaybah

Hazrat Abdur Rahman bin Abdullah bin Masood narrates that Hazrat Ali (may Allah be pleased with him) said: O people, indeed adultery is of two kinds: hidden adultery and open adultery. As for hidden adultery, it is when witnesses testify to the act of adultery, so the witnesses will be the first to throw stones, then the ruler, then the people. And open adultery is when pregnancy becomes apparent or there is a confession, so the Imam will be the first to throw a stone. The narrator says that there were some stones in your hand, so you threw a stone at that woman which struck her in the hole of her ear, so she started turning around and the people threw stones.