Hadith: Put your hand on the part of your body where you feel the pain and say: 'Bismillāh (In the name of Allah)' three times; then say seven times: 'A‘ūdhu billāhi wa qudratihi min sharri mā ajidu wa uhādhir (I seek refuge with Allah and His power from the evil that I find and fear).'

عَنْ عُثْمَانَ بْنِ أَبِي الْعَاصِ الثَّقَفِيِّ رضي الله عنه أَنَّهُ شَكَا إِلَى رَسُولِ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ وَجَعًا يَجِدُهُ فِي جَسَدِهِ مُنْذُ أَسْلَمَ، فَقَالَ لَهُ رَسُولُ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ:
«ضَعْ يَدَكَ عَلَى الَّذِي تَأَلَّمَ مِنْ جَسَدِكَ، وَقُلْ بِاسْمِ اللهِ ثَلَاثًا، وَقُلْ سَبْعَ مَرَّاتٍ أَعُوذُ بِاللهِ وَقُدْرَتِهِ مِنْ شَرِّ مَا أَجِدُ وَأُحَاذِرُ».
[صحيح] - [رواه مسلم] - [صحيح مسلم: 2202]

‘Uthmān ibn Abi al-‘Ās ath-Thaqafi (may Allah be pleased with him) reported that he complained to the Messenger of Allah (may Allah's peace and blessings be upon him) about some pain that he had been feeling in his body since embracing Islam. Thereupon, the Messenger of Allah (may Allah's peace and blessings be upon him) said to him:
"Put your hand on the part of your body where you feel the pain and say: 'Bismillāh (In the name of Allah)' three times; then say seven times: 'A‘ūdhu billāhi wa qudratihi min sharri mā ajidu wa uhādhir (I seek refuge with Allah and His power from the evil that I find and fear).'"
[Authentic hadith] - [Narrated by Muslim] - [Sahih Muslim - 2202]

Explanation

‘Uthmām ibn Abi al-‘Ās (may Allah be pleased with him) suffered from pain that was on the verge of ruining him. The Prophet (may Allah's peace and blessings be upon him), thus, went to visit him and taught him a supplication through which Allah would cure him of the illness that had affected him. He taught him to place his hand on the part where he felt the pain and say: (In the name of Allah) three times, then to repeat seven times: (I seek refuge), shelter, protection, and security (with Allah and His power from the evil that I find), i.e., the current pain, (and fear) of its occurrence in the future, referring to sorrow and apprehension, or the continuity of this illness and the spread of pain in the body.