Musannaf Ibn Abi Shayba 3:2432

Abu Khalid al-Ahmar narrated to us, from Ibn ‘Ajlan, from Ya’qub ibn ‘Abd Allah ibn al-Ashajj, from Bashir ibn Sa’id, who said: A man greeted the Prophet, peace and blessings of Allah be upon him, while he was praying, so he gestured to him with his hand as if he were forbidding him.