Muwatta Malik, Book 31, Hadith 102 (USC-MSA)

Malik related to me that he asked Ibn Shihab about a man who hired an animal, and then re-hired it out for more than what he hired it for. He said, "There is no harm in that."

وَحَدَّثَنِي مَالِكٌ، عَنِ ابْنِ شِهَابٍ، أَنَّهُ سَأَلَهُ عَنِ الرَّجُلِ، يَتَكَارَى الدَّابَّةَ ثُمَّ يُكْرِيهَا بِأَكْثَرَ مِمَّا تَكَارَاهَا بِهِ فَقَالَ لاَ بَأْسَ بِذَلِكَ ‏.‏

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also referenced under: Book 31, Hadith 1388 (In-Book)