Any Muslim servant who visits a sick person whose prescribed moment of death has not arrived and supplicates seven times:

أَسْأَلُ اللَّهَ الْعَظِيمَ رَبَّ الْعَرْشِ الْعَظِيمِ أَنْ يَشْفِيَكَ

I ask Almighty Allah, Lord of the Magnificent Throne, to make you well.

As'alullaahal-'Adheema Rabbal-'Arshil-'Adheemi 'an yashfiyaka.

…then perhaps, for this reason, Allah will cure the person (if not near Death)

At-Tirmithi, Abu Dawud. See also Al-Albani, Sahih At-Tirmithi 2/210 and Sahihul-Jami' As-Saghir 5/180.