Hadith 513790
Chapter 31: Business Transactions - كتاب البيوع
وَحَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عُمَرَ، يَقُولُ مَنْ أَسْلَفَ سَلَفًا فَلاَ يَشْتَرِطْ إِلاَّ قَضَاءَهُ .
Yahya related to me from Malik from Nafi that he heard Abdullah ibn Umar say, "If someone lends something, let the only condition be that it is repaid."
Reference Muwatta Malik 513790
USC-MSA web (English) reference : Book 31, Hadith 94