The Prophet ﷺ said: If anyone has himself cupped on the 17th, 19th and 21st it will be a remedy for every disease.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنِ احْتَجَمَ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ كَانَ شِفَاءً مِنْ كُلِّ دَاءٍ  

"The Prophet ﷺ would get cupped in his jugular veins and his upper back. And he would get cupped on the seventeenth (of the month), (or) the nineteenth, and (or) the twenty first."  

كَانَ رَسُولُ اللَّهِ ﷺ يَحْتَجِمُ فِي الأَخْدَعَيْنِ وَالْكَاهِلِ وَكَانَ يَحْتَجِمُ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ  

"The Prophet ﷺ would get cupped in his jugular veins and his upper back. And he would get cupped on the seventeenth (of the month), (or) the nineteenth, and (or) the twenty first." (Using translation from Tirmidhī 2051)   

«كَانَ رَسُولُ اللَّهِ ﷺ يَحْتَجِمُ عَلَى الْأَخْدَعَيْنِ وَكَانَ يَحْتَجِمُ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ»  

The Prophet ﷺ said: If anyone has himself cupped on the 17th, 19th and 21st it will be a remedy for every disease. (Using translation from Abū Dāʾūd 3861)   

قَالَ رَسُولُ اللهِ ﷺ مَنِ احْتَجَمَ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ كَانَ شِفَاءً مِنْ كُلِّ دَاءٍ  

[Machine] "The Messenger of Allah, ﷺ , said: The best of what you hope in (or seek protection in) is the seventeenth, nineteenth, and twenty-first, as narrated by Al-Zuhri from the Prophet, ﷺ , directly."  

رَسُولَ اللهِ ﷺ قَالَ خَيْرُ مَا تَحْتَجِمُونَ فِيهِ سَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ وَرَوَاهُ أَيْضًا الزُّهْرِيُّ عَنِ النَّبِيِّ ﷺ مُرْسَلًا  

"منِ احْتَجَمَ لِسَبْعَ عَشْرةَ مِنَ الشَّهْر وَتِسْعَ عَشْرة، وإِحْدَى وعشْرِينَ، كَان لَهُ شِفَاءً مِنْ كُلِّ دَاءٍ".  

"إِنَّ خَيْرَ ما تحتجمون فيه يَوْمُ سَبْعَ عَشَرَةَ ويَوْمُ تِسْعَ عَشَرَةَ ويومُ إِحدى وعشرين" .