Mishkat al-Masabih
Ibn ‘Abbas reported God’s messenger as saying, "No Muslim will visit another and say seven times, ‘I ask God, the Mighty, the Lord of the mighty throne, to cure you’ without his being cured, unless his time has come.” Abu Dawud and Tirmidhi transmitted it.
وَعَنِ ابْنِ عَبَّاسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " مَا مِنْ مُسْلِمٍ يَعُودُ مُسْلِمًا فَيَقُولُ سَبْعَ مَرَّاتٍ: أَسْأَلُ اللَّهَ الْعَظِيمَ رَبَّ الْعَرْشِ الْعَظِيمِ أَنْ يَشْفِيَكَ إِلَّا شُفِيَ إِلَّا أَنْ يَكُونَ قَدْ حَضَرَ أَجَلُهُ ". رَوَاهُ أَبُو دَاوُد وَالتِّرْمِذِيّ
Reference