Musnad Ahmad 25:299

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Yazid Abu Khalid, who said: I heard al-Minhal ibn ‘Amr narrating from Sa‘id ibn Jubayr, from Ibn ‘Abbas, from the Prophet, may Allah bless him and grant him peace, that he said: "There is no Muslim servant who visits a sick person whose time of death has not yet arrived, and says seven times: 'I ask Allah the Almighty, Lord of the Magnificent Throne, to heal you,' but he will be cured."