It is narrated from Muhammad bin Sirin (may Allah have mercy on him) that Shurayh (may Allah have mercy on him) used to say: "Two upright witnesses should testify that you two (i.e. the seller and the buyer) parted by mutual consent after the sale or after the option of the session (the choice to keep or cancel the sale); and if there are no such witnesses, then it is his (the claimant's) oath by Allah that you two did not part by mutual consent after the sale or after the option of the session."
Its chain is sahih (authentic), and this saying is mawquf (stopping) at Shurayh (may Allah have mercy on him).
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب القضاء والشهادات / 2190
Hadith Gradingمحدثین:إسناده صحيح، موقوف
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :قال ابن حجر: إِسْنَادُهُ صَحِيحٌ مَوْقُوفٌ عَلَى شُرَيْحٍ . » «انفرد به المصنف من هذا الطريق»