Musannaf Ibn Abi Shayba 18:1031

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Khusayf, from Mujahid, from Ibn Abbas regarding the saying: "It is as if he had slain mankind entirely." He said: "Whoever destroys it." And regarding the saying: "And whoever saves one, it is as if he had saved mankind entirely." He said: "Whoever refrains from killing it."