Sunan Abi Dawud 21724
In-book no 1220حَدَّثَنَا سُلَيْمَانُ بْنُ دَاوُدَ الْمَهْرِيُّ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي جَابِرُ بْنُ إِسْمَاعِيلَ، عَنْ عُقَيْلٍ، بِهَذَا الْحَدِيثِ بِإِسْنَادِهِ قَالَ وَيُؤَخِّرُ الْمَغْرِبَ حَتَّى يَجْمَعَ بَيْنَهَا وَبَيْنَ الْعِشَاءِ حِينَ يَغِيبُ الشَّفَقُ .
The above mentioned tradition has also been reported by 'Uqail through a different chain of narrators. He said: He would delay the evening prayer till he combined the evening and the night prayers when the twilight disappeared.