Narrated Amr bin Suhaib: On his father's authority, said that his grandfather told that the Messenger of Allah ﷺ forbade the type of transactions in which earnest money was paid. Malik said: This means, as we think--Allah better knows-that a man buys a slave or hires an animal, and he says: I give you a dinar on condition that if I give up the transaction or hire, what I gave you is yours.
Hadith Referenceسنن ابي داود / كتاب الإجارة / 3502
Hadith Takhrij« سنن ابن ماجہ/التجارات 22 (2192)، (تحفة الأشراف: 8820)، وقد أخرجہ: موطا امام مالک/ البیوع 1 (1)، مسند احمد (2/183) (ضعیف) » (اس کی سند میں انقطاع ہے ، یہ امام مالک کی بلاغات میں سے ہے)