Musnad Abu Ya'la al-Mawsili 110:146

Abu Khaythama narrated to us, Hushaym narrated to us, 'Awf narrated to us, from Ziyad ibn Husayn, from Abu al-'Aliyah, from Ibn 'Abbas, who said: The Prophet (peace be upon him) said to me, "Come, pick up for me." He said: So I picked up for him pebbles, which were the pebbles of *al-hadhf* (throwing with the thumb and index finger). When I placed them in his hand, he said, "Yes, with the likes of these. And beware of extremism in religion, for those who were before you were only destroyed by extremism in religion."