Musannaf Ibn Abi Shaybah

Hazrat Yazid bin Hurmuz (may Allah have mercy on him) says that Najdah wrote a letter to Hazrat Ibn Abbas (may Allah be pleased with them both) asking about killing children, and in his letter he wrote that indeed a knowledgeable person who was a companion of Hazrat Musa (peace be upon him) killed a child?! Yazid says that I wrote a letter with my own hand from Hazrat Ibn Abbas (may Allah be pleased with them both) to Najdah: You wrote a letter asking about killing children, and in your letter you said that indeed a knowledgeable person who was a companion of Hazrat Musa (peace be upon him), verily he killed a child?! If you also knew about children what he knew, then you too would have killed him. But you do not know. Verily, the Messenger of Allah (peace and blessings be upon him) forbade killing children. So keep away from them.