Muwatta Malik, Book 31, Hadith 41 (USC-MSA)

Yahya related to me from Malik from Abdullah ibn Dinar from Abdullah ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, said, "Someone who buys food, must not sell it until he takes possession of it."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنِ ابْتَاعَ طَعَامًا فَلاَ يَبِعْهُ حَتَّى يَقْبِضَهُ ‏" ‏ ‏.‏

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also referenced under: Book 31, Hadith 1333 (In-Book)