Muwatta Malik, Book 20, Hadith 208 (USC-MSA) ⓘ
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to pray maghrib and isha together at Muzdalifa.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُصَلِّي الْمَغْرِبَ وَالْعِشَاءَ بِالْمُزْدَلِفَةِ جَمِيعًا .
also referenced under: Book 20, Hadith 907 (In-Book)