Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says: When we found a man absent from the Fajr and Isha prayers, we would think ill of him.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Kabir, and Imam al-Bazzar also recorded it; the narrators of Imam al-Tabarani have been declared trustworthy (muwaththaqun).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2151