Al-Kāfi - Volume 5 > Dispute between Buyer and Seller
Hadith #1

1- عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ أَبِي نَصْرٍ عَنْ بَعْضِ أَصْحَابِهِ عَنْ أَبِي عَبْدِ اللهِ (عَلَيْهِ السَّلام) فِي الرَّجُلِ يَبِيعُ الشَّيْ‏ءَ فَيَقُولُ الْمُشْتَرِي هُوَ بِكَذَا وَكَذَا بِأَقَلِّ مَا قَالَ الْبَائِعُ قَالَ الْقَوْلُ قَوْلُ الْبَائِعِ مَعَ يَمِينِهِ إِذَا كَانَ الشَّيْ‏ءُ قَائِماً بِعَيْنِهِ.

1. A number of our people have narrated from Sahl ibn Ziyad from Ahmad ibn Muhammad ibn abu Nasr who has said the following: “About the case of a man who sells something and the buyers says, ‘I pay so and so’ which is less than what the seller wants, abu ‘ Abd Allah, ‘Alayhi al-Salam, has said, The words of seller are accepted on oath if the merchandise still exists.”’