Musnad Abu Ya'la al-Mawsili 110:103

Harun ibn Ma'ruf narrated to us, Abdullah ibn Wahb narrated to us, he said: Amr informed me, from Abd Rabbih ibn Sa'id, he said: Al-Minhal ibn Amr narrated to me, and once he said: Sa'id ibn Jubayr informed me, from Abdullah ibn al-Harith, from Ibn Abbas, he said: When the Messenger of Allah (peace and blessings of Allah be upon him) would visit a sick person, he would sit at his head, then he would say seven times: "I ask Allah the Almighty, Lord of the Magnificent Throne, to heal you." He said: If there is a delay in his appointed time (of death), he will be cured of that pain of his.