Hadith: Whoever visits a sick person whose time of death has not yet come, and says seven times in his presence: 'As’alullāh al-‘azhīm Rabb al-‘arshi al-‘azhīm an yashfiyak (I ask Allah the Great, Lord of the great Throne, to cure you),' except that Allah will cure him of that sickness

عَنِ ابْنِ عَبَّاسٍ رضي الله عنهما عَنِ النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«مَنْ عَادَ مَرِيضًا، لَمْ يَحْضُرْ أَجَلُهُ فَقَالَ عِنْدَهُ سَبْعَ مِرَارٍ: أَسْأَلُ اللَّهَ الْعَظِيمَ رَبَّ الْعَرْشِ الْعَظِيمِ أَنْ يَشْفِيَكَ، إِلَّا عَافَاهُ اللَّهُ مِنْ ذَلِكَ الْمَرَضِ».
[صحيح] - [رواه أبو داود والترمذي وأحمد] - [سنن أبي داود: 3106]

Ibn ‘Abbās (may Allah be pleased with him and his father) reported that the Prophet (may Allah's peace and blessings be upon him) said:
"Whoever visits a sick person whose time of death has not yet come, and says seven times in his presence: 'As’alullāh al-‘azhīm Rabb al-‘arshi al-‘azhīm an yashfiyak (I ask Allah the Great, Lord of the great Throne, to cure you),' except that Allah will cure him of that sickness."
[Authentic hadith] - [Narrated by Abu Daoud & At-Termedhy & Ahmad] - [Sunan Abu Daoud - 3106]

Explanation

The Prophet (may Allah's peace and blessings be upon him) informed that no Muslim visits a sick Muslim whose time of death has not yet come, then the visitor supplicates for the sick person, saying: (I ask Allah the Great) in His essence, attributes, and actions, (Lord of the great Throne, to cure you), and repeats it for him seven times except that Allah will cure him of that sickness.