Did the Prophet (blessings and peace of Allah be upon him) Fast the First Ten Days of Dhul-Hijjah?
Question

I have read on your website a number of fatwas which encourage people to fast the first ten days of Dhul-Hijjah and say that doing so is Sunnah, but I have also read a hadeeth from ‘Aa’ishah (may Allah be pleased with her) which says the following: 
Abu Bakr ibn Naafi‘ al-‘Abdi told me: ‘Abd ar-Rahmaan told us: Sufyaan told us, from al-A‘mash, from Ibraaheem, from al-Aswad, from ‘Aa’ishah (may Allah be pleased with her), that the Prophet (blessings and peace of Allah be upon him) did not fast the first ten days (of Dhul-Hijjah). (Narrated by Muslim, 2847)
 Does this mean that fasting the first ten days of Dhul-Hijjah was something that was not known to some of the Sahaabah, including ‘Aa’ishah, or does it mean that the Prophet (blessings and peace of Allah be upon him) used to fast it sometimes and not at other times?
Praise be to Allah.Fasting the first nine days of Dhul-Hijjah is recommended
It is encouraged (mustahabb) to fast the first nine days of Dhul-Hijjah . This is the view of the majority of scholars, because of the report narrated by Ibn ‘Abbaas (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “There are no days during which doing righteous deeds is more beloved to Allah than these days” – meaning the first ten days (of Dhul-Hijjah). They said: O Messenger of Allah, not even jihad for the sake of Allah? He said: Not even jihad for the sake of Allah, unless a man goes out, offering himself and his wealth, and does not come back with any of that.” (Narrated by al-Bukhaari (969), Abu Dawood (2438 – this version   was narrated by him), at-Tirmidhi (757) and Ibn Maajah (1727). 
Undoubtedly fasting is one of the best of righteous deeds, and it is included among the righteous deeds that are encouraged during these blessed days, according to this hadeeth. 
How scholars interpreted the narration of ‘Aishah that the Prophet (blessings and peace of Allah be upon him) did not fast the first ten days of Dhul-Hijjah
With regard to the hadeeth of ‘Aa’ishah (may Allah be pleased with her), according to which the Prophet (blessings and peace of Allah be upon him) did not fast these ten days, which was narrated by Muslim, it is contradicted by the report narrated by Abu Dawood (2437) from Hunaydah ibn Khaalid (may Allah be pleased with him) from his wife, from one of the wives of the Prophet (blessings and peace of Allah be upon him, and may He be pleased with all of them), who said: The Messenger of Allah (blessings and peace of Allah be upon him) used to fast the first nine days of Dhul-Hijjah, the day of ‘Ashoora’ and three days of every month. Shaykh al-Albaani (may Allah have mercy on him) said: Its isnaad is saheeh, in Saheeh Sunan Abi Dawood. 
There are several scholarly opinions concerning this issue, including the following: 

That ‘Aa’ishah (may Allah be pleased with her) spoke of what she knew, and others said something different to what she said. The word of one who knows something is to be taken as proof rather than the word of the one who does not know, and that which is affirmed takes precedence over that which is negated. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 
Imam Ahmad (may Allah have mercy on him) said concerning the contradiction between these two hadeeths: that which is affirmed takes precedence over that which is negated. End quote from Ash-Sharh al-Mumti‘ (6/154) 

Words take precedence over actions; the hadeeth of Ibn ‘Abbaas reports words that he heard, whereas the hadeeth of ‘Aa’ishah reports actions (or the absence thereof). Hence the words take precedence because of the possibility that the action (or the absence thereof) was specific to a particular situation, or was due to a legitimate excuse, and the like. 

Shaykh al-Albaani (may Allah have mercy on him) said: 
“The words of the Messenger (blessings and peace of Allah be upon him) to this ummah are instructions to everyone. As for the actions that he did, they may be instructions to everyone, if there is no indication to the contrary, or they may be something that was applicable only to him (blessings and peace of Allah be upon him). 

It may be that the Prophet (blessings and peace of Allah be upon him) did not fast these days because of an excuse such as travelling or sickness or anything else that may have distracted him from that, and the like, so the hadeeth of ‘Aa’ishah (may Allah be pleased with her) speaks of what she saw in that regard.”

An-Nawawi (may Allah have mercy on him) said: 
With regard to the hadeeth of ‘Aa’ishah, who said: I never saw the Messenger of Allah (blessings and peace of Allah be upon him) fasting during the ten days – and according to another report: he did not fast the ten days – both of which were narrated by Muslim in his Saheeh, the scholars said: This is to be understood as meaning that she did not see him do that; it does not necessarily mean that he did not do that particular thing, because he (blessings and peace of Allah be upon him) used to spend one day out of nine with her, and the other days with the other Mothers of the Believers (may Allah be pleased with them). Or perhaps he (blessings and peace of Allah be upon him) used to fast some of those days sometimes, and all of them at other times, and he did not fast them sometimes for a reason such as travel or sickness and so on. In this way we may reconcile between the hadeeths.” (Al-Majmoo‘, 6/441). 
Ash-Shawkaani (may Allah have mercy on him) said: 
“We have quoted above hadeeths which highlight the virtue of doing good deeds in the first ten days of Dhul-Hijjah in general, and fasting is included in that. With regard to the report narrated by Muslim from ‘Aa’ishah, according to which she said: I never saw the Messenger of Allah (blessings and peace of Allah be upon him) fasting during the ten days, the scholars said: What is meant is that he did not fast those days for a reason such as sickness, travel and the like. Or the fact that she did not see him fasting does not necessarily imply that he did not fast. Moreover, it is proven that he said words indicating that it is prescribed to fast on those days, so the suggestion that he did not do it does not undermine the hadeeth.” (Nayl al-Awtaar, 4/283) 

It may be that the Prophet (blessings and peace of Allah be upon him) did not fast these days on some occasions, because he liked to do things sometimes and refrain from them sometimes for fear that they may be made obligatory for the ummah, as in the case when he stopped praying Taraweeh in congregation in Ramadan. By refraining from doing something and taking a lenient view concerning it he showed compassion towards the ummah. 

Al-Bukhaari (1128) and Muslim (718) narrated from ‘Aa’ishah (may Allah be pleased with her) that she said: I never saw the Messenger of Allah (blessings and peace of Allah be upon him) praying the nafil prayer of Duha but I used to do it. If the Messenger of Allah (blessings and peace of Allah be upon him) gave up an action that he liked to do, it was for fear that the people would do it and it would be made obligatory for them. 
Al-Haafizh (may Allah have mercy on him) said: 
“It – namely the hadeeth of Ibn ‘Abbaas – was quoted as evidence for the virtue of fasting the first ten days of Dhul-Hijjah, because fasting is included under the heading of good deeds. That is not contradicted by the report narrated by Abu Dawood and others from ‘Aa’ishah, who said:  I never saw the Messenger of Allah (blessings and peace of Allah be upon him) fasting the ten days. It may be that this was because he used to give up an action that he liked to do for fear that it might be made obligatory upon his ummah.” (Fath al-Baari, 2/460) 

It was said that the hadeeth which speaks of the Prophet (blessings and peace of Allah be upon him) fasting the first nine days of Dhul-Hijjah is da‘eef and cannot be quoted as evidence. There was a difference of opinion concerning Hunaydah [one of the narrators]. It was narrated from him, from his wife, from one of the wives of the Prophet (blessings and peace of Allah be upon him); and it was narrated from him from Hafsah, the wife of the Prophet (blessings and peace of Allah be upon him); and it was narrated from him from his mother from Umm Salamah. (Nasb ar-Raayah, 2/157) 

But there remains the general meaning of the hadeeth of Ibn ‘Abbaas to indicate that it is prescribed to fast during these days. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked:
Is there any report from the Messenger (blessings and peace of Allah be upon him) about fasting all the first ten days of Dhul-Hijjah?
He replied: 
“There is a report from the Prophet (blessings and peace of Allah be upon him) which speaks in more general terms than fasting on these days. He encouraged people to fast on these days when he said: “There are no days during which doing righteous deeds is more beloved to Allah than these ten days.” They said: O Messenger of Allah, not even jihad for the sake of Allah? He said: Not even jihad for the sake of Allah, unless a man goes out, offering himself and his wealth, and does not come back with any of that.” It is well-known that fasting is one of the best of righteous deeds. 
As for whether he himself did that, there are two hadeeths which speak of that: the hadeeth of ‘Aa’ishah and the hadeeth of Hafsah. As for the hadeeth of ‘Aa’ishah, she said: I never saw the Prophet (blessings and peace of Allah be upon him) fasting the ten days. As for the hadeeth of Hafsah, she said: The Prophet (blessings and peace of Allah be upon him) never omitted to fast them. When there is a contradiction between two hadeeths, one of them affirming a thing and the second denying it, then the one which affirms it takes precedence over the one which denies it. Hence Imam Ahmad said: The hadeeth of Hafsah affirms it and the hadeeth of ‘Aa’ishah denies it, but the one which affirms it takes precedence over the one which denies it. 
I would like to give you a basic principle: If the Sunnah gives a word, then take what that word indicates. As for action, it is not essential for us to know whether the Messenger or the Sahaabah did that thing. If we were to say: we will not accept a report unless we know that the Sahaabah did it, we would miss out on a lot of acts of worship. But here we have a word which is evident proof and has reached us, so we must do what it implies, regardless of whether we know that the people did it in the past or not.” (Liqa’ al-Baab al-Maftooh, 92/12) 
For more information, see the answer to question no. 145046
And Allah knows best.