Al-Kāfi
Hadith 7095- عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنْ فَضَالَةَ بْنِ أَيُّوبَ عَنْ مُعَاوِيَةَ بْنِ عَمَّارٍ قَالَ قُلْتُ لأبِي عَبْدِ اللهِ (عَلَيْهِ السَّلام) الرَّجُلُ يَجِيئُنِي يَطْلُبُ الْمَتَاعَ الْحَرِيرَ وَلَيْسَ عِنْدِي مِنْهُ شَيْءٌ فَيُقَاوِلُنِي وَأُقَاوِلُهُ فِي الرِّبْحِ وَالأجَلِ حَتَّى يَجْتَمِعَ عَلَيَّ شَيْءٌ ثُمَّ أَذْهَبُ فَأَشْتَرِي لَهُ الْحَرِيرَ وَأَدْعُوهُ إِلَيْهِ فَقَالَ أَرَأَيْتَ إِنْ وَجَدَ بَيْعاً هُوَ أَحَبُّ إِلَيْهِ مِمَّا عِنْدَكَ أَيَسْتَطِيعُ أَنْ يَنْصَرِفَ إِلَيْهِ وَيَدَعَكَ أَوْ وَجَدْتَ أَنْتَ ذَلِكَ أَتَسْتَطِيعُ أَنْ تَنْصَرِفَ عَنْهُ وَتَدَعَهُ قُلْتُ نَعَمْ قَالَ لا بَأْسَ.
5. A number of our people have narrated from Ahmad ibn Muhammad from al-Husayn ibn Sa‘id from Fadalah ibn Ayyub from Mu‘awiyah ibn ‘Ammar who has said the following: “This is concerning my question before abu ‘Abd Allah (a.s.), about the case of a man who comes to me and asks for certain goods of silk but I do not have anything as such, ‘Consider if he finds a better deal than this; can he change and go for that deal instead of the deal with you and can the same thing apply to you also?’ I replied, ‘Yes, - that can happen.’ He (the Imam) said, Tt then is lawful.’”