On it being disliked to leave the mosque after the adhan without reason before the obligatory prayer has been prayed

Riyad as-Salihin (The Meadows of the Righteous)

by Imam Nawawi

358. Chapter: On it being disliked to leave the mosque after the adhan without reason before the obligatory prayer has been prayed

1785. Abu'sh-Sha'tha' said, "We were sitting with Abu Hurayra in the mosque and the mu'adhdhin called the adhan. A man in the mosque began to walk out and Abu Hurayra's eye followed him until he had left the mosque. Abu Hurayra then said, 'This man has rebelled against Abu'l-Qasim.'" [Muslim]