مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2133
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn 'Abbas (رضي الله عنه) that the Prophet (ﷺ) said: "There is no Muslim who visits a sick person whose time has not yet come, and says seven times, 'I ask Allah the Almighty, Lord of the Mighty Throne, to heal you,' but he will be healed."
Musnad Ahmad 2137A saheeh hadeeth]