What is the Sunnah for the Imam if he enters the mosque before or after the Adhan?

The guidance of the Prophet, peace and blessings be upon him, regarding going out to the mosque was just before the Iqamah; when Bilal saw him, he would call the Iqamah for prayer. Sometimes Bilal would go to him, and then they would go out together, and he would call the Iqamah. Thus, the Sunnah is for the Imam to remain in his home, and when the time for Iqamah arrives, he goes out to the mosque to lead the people in prayer. If the Imam arrives early at the mosque, it is legislated for him to pray Tahiyyat al-Masjid (greeting the mosque) and the pre-prayer Sunnah if he has not prayed it at home, then he sits in any part of the mosque. As for the Imam sitting in the mihrab before the prayer, it is disliked, and it might cause him to feel elevated or arrogant, or lead to the worshippers facing him in their prayers, which is disliked. The Imam should sit in another place in the mosque if he arrives early. An exception to this is the Imam sitting in his place after the Fajr prayer until the sun rises, as this is recommended.