I used to sell camels at al-Baqi. I would sell for dinars and take dirhams in their place, and I would sell for dirhams and take dinars in their place. So I came to the Prophet ﷺ as he was about to enter his apartment, and I caught hold of his garment and asked him about this.He said, "When you take one of the two in place of the other, do not part from your companion while there is still anything outstanding in the transaction between you."
حدثنا يحيى بن آدم حدثنا إسرائيل عن سماك عن سعيد بن جبير
كنت أبيع الإبل بالبقيع فأبيع بالدنانير وآخذ الدراهم وأبيع بالدراهم وآخذ الدنانير فأتيت النبي ﷺ وهو يريد أن يدخل حجرته فأخذت بثوبه فسألته فقال إذا أخذت واحدا منهما بالآخر فلا يفارقنك وبينك وبينه بيع