[Machine] The Prophet ﷺ said: "What is the best action in the sight of Allah during the ten days of Dhul Hijjah?" They said, "O Messenger of Allah, not even Jihad in the cause of Allah?" He said, "Not even Jihad in the cause of Allah, except for a man who goes out with himself and his wealth in the cause of Allah and does not return with anything." This is the wording of the narration of Shu'bah, and in the narration of Abu Mu'awiyah it is stated: The Messenger of Allah ﷺ said, "There are no days in which righteous deeds are more beloved to Allah than these days," meaning the ten days, and the remaining part is the same in meaning.  

أَنَّ النَّبِيَّ ﷺ قَالَ مَا الْعَمَلُ فِي أَيَّامٍ أَفْضَلَ مِنْهُ فِي عَشْرِ ذِي الْحِجَّةِ قَالُوا يَا رَسُولَ اللهِ وَلَا الْجِهَادُ فِي سَبِيلِ اللهِ قَالَ وَلَا الْجِهَادُ فِي سَبِيلِ اللهِ إِلَّا رَجُلٌ خَرَجَ بِنَفْسِهِ وَمَالِهِ فِي سَبِيلِ اللهِ ثُمَّ لَا يَرْجِعُ مِنْ ذَلِكَ بِشَيْءٍ لَفْظُ حَدِيثِ شُعْبَةَ وَفِي رِوَايَةِ أَبِي مُعَاوِيَةَ قَالَ قَالَ رَسُولُ اللهِ ﷺ مَا مِنْ أَيَّامٍ الْعَمَلُ الصَّالِحُ فِيهَا أَحَبُّ إِلَى اللهِ مِنْ هَذِهِ الْأَيَّامِ يَعْنِي أَيَّامَ الْعَشْرِ وَالْبَاقِي بِمَعْنَاهُ  

Hunaydah ibn Khalid narrated from his wife on the authority of one of the wives of the Prophet ﷺ who said: The Messenger of Allah ﷺ used to fast the first nine days of Dhul-Hijjah, Ashura' and three days of every month, that is, the first Monday (of the month) and Thursday. (Using translation from Abū Dāʾūd 2437)   

عَنْ بَعْضِ أَزْوَاجِ النَّبِيِّ ﷺ قَالَتْ كَانَ رَسُولُ اللهِ ﷺ يَصُومُ تِسْعَ ذِي الْحِجَّةِ وَيَوْمَ عَاشُورَاءَ وَثَلَاثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ أَوَّلَ اثْنَيْنِ مِنَ الشَّهْرِ وَالْخَمِيسَ تَعْنِي وَيَوْمًا آخَرَ وَرَوَاهُ أَبُو دَاوُدَ عَنْ مُسَدَّدٍ  

[Machine] I have never seen the Messenger of Allah ﷺ fasting during the ten (days of) Dhul-Hijjah.  

مَا رَأَيْتُ رَسُولَ اللهِ ﷺ صَائِمًا فِي الْعَشْرِ قَطُّ