Masjid Namirah is a well known Masjid in Arafat area. It is mentioned that this Masjid was built on the place were the Prophet Muhammad (SAWA) gave his famous sermon in Arafah when he performed Hajj on the year 10 after Hijra which is called Hajjatul Wadaa' (The Welfare Hajj).
Masjid Namirah is important for the followers of Ahlul Bayt (AS) as it is one of the places where the Prophet (SAWA) visited and gave a sermon. The Prophet (SAWA) prayed Dhuhr and Asr prayers together. All Muslims admit and accept this fact. No one can claim the the Prophet prayed Asr before its time. It means hat he tme of As starts immediately after performing Dhuhr Prayer.
Till now, all Muslims pray Dhuhr and Asr together in Arafah. This Prophetic worship itself is another evidence that what Shi'a Muslims practice is completely authentic and it is from the Prophet Muhammad (SAWA).