Saad ibn Mu’adh was a tribal head or leader of the Banu Aus tribe in Medina and he not only converted to Islam but he was among the one who empowered Islam’s establishment on the earth that is the reason he and his tribe is called as Ansar (The Helpers of Allah’s Deen).
The first Islamic state was established due to the Nusrah and allegiance given to the Prophet by Hazrat Saad and the other tribe Khazraj. Therefore the honor given by the Prophet to Saad ibn Muadh was exceptional. On the death of Saad ibn Muadh the Prophet peace be upon Him exclaimed that the throne (Aasmaan) of Allah moved or as if in Urdu ‘The Arsh of Allah moved’, some interpret as if aasman Hil gaya.
Whatever the metaphoric relation is but the fact is this was the honor, and admiration which the last Prophet peace be upon him attributed towards the empowerment of Islam (Nusrah) by Saad ibn Muadh is exceptional.
The hadith in Sahih Bukhari recorded in volume five book fifty eight and number one hundred and forty seven says as per the narration of Jabir: He listened Prophet peace be upon Him saying “The Throne (Arsh or Aasmaan) (of Allah) tremble at the decease of Saad bin Muadh.” In the course of an additional faction of narrators, Jabir exclaimed, “I listened the Prophet peace be upon Him expressing, ‘The Throne (Arsh or Aasmaan) of the Beneficent shook for the reason of the passing away of Saad bin Muadh.”