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 ‏"‏ ‏.‏