Some people of innovations are trying to install some doubt on Muslims by saying the hadith which was reported by Ibn Abbas on the the prophet arriving in Madina and seeing Jews fasting on Ashura.They say Ibn Abbas was only four years old during that time, Abu Musa was not even a Muslim during that time,the same applied to Abu Hurayra and Muawiya.How can we respond to this people? Jazakallahu Khairan.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

It is not a wonder that the people of innovations would question the authenticity of the Hadeeth regarding fasting on the Day of ‘Ashooraa' since they question the authenticity of even greater matters.

Whenever Ibn ‘Abbaas, Abu Hurayrah, Abu Moosa, or any other Companion reports an incident that he has not witnessed himself or a Hadeeth that he has not heard directly from the Prophet, sallallaahu ‘alayhi wa sallam, the scholars classify it as Mursal As-Sahaabi (i.e. a Hadeeth referred to the Prophet by a Companion who did not hear it directly from the Prophet ), and it may be used as textual evidence. That is because if the Companion relates an incident that he has not witnessed himself, then he has heard it from another Companion who had witnessed it as a Companion in all likelihood would only relate from another Companion, and all the Companions are regarded as trustworthy reporters of Hadeeth.

Al-Haafith As-Suyooti wrote in relation to Mursal As-Sahaabi Hadeeth: "Mursal As-Sahaabi is when the Companion reports something that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, did or the like of that, but it is known that he did not witness it because he was young at the time or had not yet embraced Islam. It is classified as authentic according to the preponderant opinion of the Shaafi‘i School of Fiqh and this view is adopted by the majority of the Shaafi‘is and other Schools of Fiqh. The Hadeeth scholars, who set the criteria for authenticity, and who maintained that a Mursal Hadeeth is weak (in general), agreed that Mursal As-Sahaabi Ahaadeeth are accepted and authoritative (and not classified as weak like the Mursal Hadeeth from Taabi‘is). There are many examples in As-Saheehayn (Al-Bukhari and Muslim) of such reports because most of the narrations cited therein are reported on the authority of Companions and all of them are trustworthy and reliable reporters. The Companions rarely narrate from non-Companions, and if they do, they clarify that." [Tadreeb Ar-Raawi]

Finally, we advise the Muslims who lack adequate knowledge not to engage in arguments with the people of religious innovations or even expose themselves to the doubts they raise as they may affect their hearts and they may not find someone to help them get rid of such doubts. We implore Allaah for safety and protection from such peril.

Allaah Knows best.