Sunan Abi Dawud, Hadith 417 ⓘ
Salamah b. al-Akwa' said: The Prophet used to say the Maghrib prayer immediately after the sun had set when its upper side would disappear.
حَدَّثَنَا عَمْرُو بْنُ عَلِيٍّ، عَنْ صَفْوَانَ بْنِ عِيسَى، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، عَنْ سَلَمَةَ بْنِ الأَكْوَعِ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يُصَلِّي الْمَغْرِبَ سَاعَةَ تَغْرُبُ الشَّمْسُ إِذَا غَابَ حَاجِبُهَا .
also referenced under: Hadith 417 (DarusSalam) & Book 2, Hadith 417 (USC-MSA)