It is narrated from Sayyiduna al-Fadl bin Abbas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said on the evening of Arafah and the morning of Muzdalifah, when they set off: "Adopt calm and tranquillity." And he was holding back his she-camel until he reached the valley of Muhassir, and he said: "You must use small pebbles, the kind with which the Jamarat are stoned."
Hadith Referenceالمعجم الكبير للطبراني / باب الفاء / 15782