Musnad Ahmad 106:1

Yahya ibn Sa'id narrated to us, he said: Isma'il narrated to us, he said: Qays narrated to us, from his father, who said: "He came while the Messenger of Allah, peace and blessings of Allah be upon him, was delivering a sermon, so he stood in the sun. He (the Prophet) ordered him, so he was moved to the shade."