Al-Kāfi
Hadith 10895- وَعَنْهُمَا عَنِ ابْنِ مَحْبُوبٍ عَنْ أَبِي وَلادٍ عَنْ أَبِي عَبْدِ اللهِ (عَلَيْهِ السَّلام) وَغَيْرِهِ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ السَّلام) قَالُوا قَالا لا بَأْسَ بِأَجْرِ السِّمْسَارِ إِنَّمَا هُوَ يَشْتَرِي لِلنَّاسِ يَوْماً بَعْدَ يَوْمٍ بِشَيْءٍ مَعْلُومٍ وَإِنَّمَا هُوَ مِثْلُ الأجِيرِ.
5. It is narrated from the two of them from ibn Mahbub from abu Wallad and others who has said the following: “They have said that abu Ja‘far (a.s.), has said, ‘Payment for brokerage fee to a broker who buys goods for people day after day is not unlawful.’”