Musnad Ahmad 1795

It was narrated from al-Fadl bin "Abbas - who rode seated behind the Prophet (ﷺ) - that he said on the evening of "Arafah and the morning of Muzdalifah to the people as they were moving on: "Keep calm.” And he was reining in his she-camel until, when he entered Muhassir, which is part of Mina, he said: “Pick up small pebbles (the size of broad beans) with which to stone the Jamrah.” And the Messenger of Allah (ﷺ) continued to recite the Talbiyah until he stoned the ļamrah.