It is reported about Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he saw some people sitting with their backs leaning against the qiblah wall of the mosque between the adhan and the iqamah of Fajr. Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "Do not be an obstacle between the angels and their prayer."
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators have been deemed trustworthy (muwaththaq).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2036