Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
suyuti:1436a

"If two (separate) authorized persons make a sale (of the same thing), then the first transaction is the one that is valid. " (Using translation from Ibn Mājah 2191)   

السيوطي:١٤٣٦a

"إذَا باعَ المُجيزَانِ فَهُو لْلأَوَّلِ".  

[هـ] ابن ماجة عن سمرة

See similar narrations below:

Collected by Ibn Mājah
ibnmajah:2191al-Ḥusayn b. Abū al-Sarī al-ʿAsqalānī And Muḥammad b. Ismāʿīl > Wakīʿ > Saʿīd b. Bashīr > Qatādah > al-Ḥasan > Samurah

"If two (separate) authorized persons make a sale (of the same thing), then the first transaction is the one that is valid. "  

ابن ماجة:٢١٩١حَدَّثَنَا 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 ﷺ إِذَا بَاعَ الْمُجِيزَانِ فَهُوَ لِلأَوَّلِ