Sunan Ibn Majah, Volume 3, Book 12, Hadith 2191 (DarusSalam) ⓘ
It was narrated from Samurah that the Messenger of Allah, said: "If two (separate) authorized persons make a sale (of the same thing), then the first transaction is the one that is valid. "
حَدَّثَنَا الْحُسَيْنُ بْنُ أَبِي السَّرِيِّ الْعَسْقَلاَنِيُّ، وَمُحَمَّدُ بْنُ إِسْمَاعِيلَ، قَالاَ حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا سَعِيدُ بْنُ بَشِيرٍ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ سَمُرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِذَا بَاعَ الْمُجِيزَانِ فَهُوَ لِلأَوَّلِ " .
also referenced under: Hadith 2191 (Reference) & Book 12, Hadith 2275 (In-Book)