Man Lā Yaḥḍuruh al-Faqīh
Hadith 6973814 - وَ قَالَ عَلَيْهِ اَلسَّلاَمُ : فِي اَلرَّجُلِ يَبِيعُ اَلْمَمْلُوكَ وَ يَشْتَرِطُ عَلَيْهِ أَنْ يَجْعَلَ لَهُ شَيْئاً قَالَ "يَجُوزُ".
Hadith.3814 - Imam (as) said regarding a man who sells a slave and stipulates upon the buyer to give him something: "It is permissible."