Sayyiduna Abu Hurayrah (may Allah be pleased with him) says: Rain fell on the day of Eid, so the Prophet (peace and blessings be upon him) led them in the Eid prayer in the mosque.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6257
Uthman bin Abd al-Rahman al-Taymi (may Allah have mercy on him) says: Aban bin Uthman (may Allah have mercy on him) was the governor of Madinah. On the night of Eid al-Fitr there was heavy rain. He gathered the people in the mosque and did not go out to the Eid prayer ground in which Eid al-Fitr and Eid al-Adha were prayed. Then he said to Abdullah bin Amir bin Rabi'ah (may Allah be pleased with him): Tell the people what you told me. So Abdullah bin Amir (may Allah be pleased with him) said: In the time of Sayyiduna Umar (may Allah be pleased with him) it rained, and the people held back from going to the prayer ground. Sayyiduna Umar (may Allah be pleased with him) gathered them in the mosque and led them in prayer. Then he stood on the pulpit and said: O people! The Messenger of Allah (peace and blessings be upon him) used to take the people out to the prayer ground and lead them in prayer, because that was easier for them and gave them more room, and the mosque could not hold them. He said: So when there is rain like this, the mosque is easier.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6258