Musnad Ahmad 1153:246

Yahya narrated to us, from Hisham, who said: My father informed me, from Aisha, that the Prophet, peace and blessings of Allah be upon him, used to command the killing of the *dhu al-tufyatayn* (the one with two stripes). He said: "It affects the pregnancy (or the fetus), and it seeks out the eyesight."