حَدَّثَنَا هَاشِمٌ حَدَّثَنَا لَيْثٌ حَدَّثَنِي نَافِعٌ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ قَالَ إِذَا تَبَايَعَ الرَّجُلَانِ فَكُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا فَكَانَا جَمِيعًا وَيُخَيِّرُ أَحَدُهُمَا الْآخَرَ فَإِنْ خَيَّرَ أَحَدُهُمَا الْآخَرَ فَتَبَايَعَا عَلَى ذَلِكَ وَجَبَ الْبَيْعُ وَإِنْ تَفَرَّقَا بَعْدَ أَنْ تَبَايَعَا وَلَمْ يَتْرُكْ وَاحِدٌ مِنْهُمَا الْبَيْعَ فَقَدْ وَجَبَ الْبَيْعُ
مسند امام احمد بن حنبل · Hadith 6006
It was narrated from 'Abdullah ibn 'Umar from the Messenger of Allah (PBUH) that he said: "When two men enter into a transaction, each of them has the option (of cancelling it) so long as they have not yet separated and are still together, and neither of them is asking the other to decide. If one of them asks the other to decide, then they decide (i.e., they agree to the transaction), then the transaction is binding. If they separate after making the agreement and neither of them changes his mind about the transaction, then the transaction is binding."
Sanad
حَدَّثَنَا هَاشِمٌ حَدَّثَنَا لَيْثٌ حَدَّثَنِي نَافِعٌ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ