It was narrated from 'Uqbah bin 'Amir or Samurah bin Jundab that the Messenger of Allah (ﷺ) said:
"Any man who sells to two men, it is for the one who was first."[1] (ID)
English reference (ID): Vol. 3, Book 12, Hadith 2190 (ID)
Arabic reference (ID): Book 12, Hadith 2274 (ID)