It is narrated from Sayyiduna Ali (may Allah be pleased with him) that once a mule was presented to the Prophet (peace and blessings be upon him) as a gift. I asked, "What is this?" He replied, "It is a mule. Is it male or female?" I asked, "From which lineage does it come?" He said, "A donkey is made to mount a mare, and the result is this mule." I said, "Then should I not also make such-and-such donkey mount such-and-such mare?" He said, "No, this is done by those who are ignorant."
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 766
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لضعف شريك وجهالة على بن علقمة