Hadith 513620
Chapter 31: Business Transactions - كتاب البيوع
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ رَجُلاً، قَالَ لِرَجُلٍ ابْتَعْ لِي هَذَا الْبَعِيرَ بِنَقْدٍ حَتَّى أَبْتَاعَهُ مِنْكَ إِلَى أَجَلٍ فَسُئِلَ عَنْ ذَلِكَ عَبْدُ اللَّهِ بْنُ عُمَرَ فَكَرِهَهُ وَنَهَى عَنْهُ .
Yahya related to me from Malik that he had heard that a man said to another, "Buy this camel for me immediately so that I can buy him from you on credit." Abdullah ibn Umar was asked about that and he disapproved of it and forbade it.
Reference Muwatta Malik 513620
USC-MSA web (English) reference : Book 31, Hadith 73