The Prophet ﷺ used to go out on the day of Eid al-Fitr and Eid al-Adha to the prayer ground, which was a place in Madinah, and the first thing he would begin with was the prayer.Abu Saeed said, "The people continued on this practice until I went out with Marwan, who was the governor of Madinah, on an Eid al-Adha or Eid al-Fitr. When we arrived at the prayer ground, there was a pulpit that Kathir bin Salt had built."
كان النبي ﷺ يخرج يوم الفطر والأضحى إلى المصلى (وهو موضع في المدينة) فأول شيء بدأ به الصلاة. قال أبو سعيد: فلم يزل الناس على ذلك حتى خرجت مع مروان- وهو أمير المدينة- في، أضحى، أو فطر. فلما أتينا المصلى إذا منبر بناه كثير بن الصلت.
Bukhari narrated it in the Book of the Two Eids (956), and Muslim in the Book of the Two Eids (889), both through the route of Iyad bin Abdullah bin Abu Sarh, from Abu Saeed Khudri, who mentioned it, with the wording being Bukhari's. In Muslim's wording, "Then there was Kathir bin Salt, who had built a pulpit from clay and mud brick."Kathir bin Salt was singled out for building the pulpit at the prayer ground because his house was adjacent to the prayer ground, and it contained the landmark that Ibn Abbas refers to in his statement, "Until the Prophet ﷺ reached the landmark near the house of Kathir bin Salt, then he prayed and then delivered a sermon." Bukhari (977).Ibn Saad said, "The house of Kathir bin Salt was in the direction of the qiblah from the prayer ground during the two Eids, and it overlooked the valley bed of Bathan, the wadi in the middle of Madinah." End of quote.Kathir bin Salt built his house some time after the Prophet ﷺ, but since it became well known in that area, the prayer ground came to be described by its proximity to it. Kathir bin Salt Kindi was a senior Tabii, born during the era of the Prophet ﷺ. He and his two brothers came to Madinah after the Prophet's time and settled there, and he formed an alliance with Banu Jumah. Fath al-Bari (2/449).This hadith is evidence that it is sunnah for the Eid prayer to be performed in open ground outside of buildings, and that all towns are equal in this regard, except for the Sacred House of Allah, which has a special distinction such that its people do not go out to open ground for it. It is permissible to perform the Eid prayer in the congregational masjid due to an excuse, such as rain, strong wind, fear for safety, the absence of a designated place for it, or other similar excuses.