Riyad us Saliheen: Hadith 906

The Prophet (ﷺ) said, "He who visits a sick person who is not on the point of death and supplicates seven times: As'alullahal-'Azima Rabbal-'Arshil-'Azimi, an yashfiyaka (I beseech Allah the Great, the Rubb of the Great Throne, to heal you), Allah will certainly heal him from that sickness."

[Abu Dawud and At- Tirmidhi].