(44) The Book of Financial Transactions
كتاب البيوع
(96) Chapter: If A Man Sells An Item And A Third Party Has More Right To It
(96) باب الرَّجُلِ يَبِيعُ السِّلْعَةَ فَيَسْتَحِقُّهَا مُسْتَحِقٌّ ‏‏
Sunan an-Nasa'i 4682 
It was narrated from Sammurah that the Messenger of Allah said:
"If a woman is married off by two guardians, then the first marriage is the one that counts, and if a man sells something to two men, it belongs to the first one."
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا غُنْدَرٌ، عَنْ شُعْبَةَ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ سَمُرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ أَيُّمَا امْرَأَةٍ زَوَّجَهَا وَلِيَّانِ فَهِيَ لِلأَوَّلِ مِنْهُمَا وَمَنْ بَاعَ بَيْعًا مِنْ رَجُلَيْنِ فَهُوَ لِلأَوَّلِ مِنْهُمَا ‏"‏ ‏.‏
Grade :  Hasan (Darussalam)
Reference : Sunan an-Nasa'i 4682
In-book reference : Book 44, Hadith 234
English translation : Vol. 5, Book 44, Hadith 4686