Answer to a question from tonight's class:

Renting a stallion for breeding purposes falls under contracts of uncertainty (bay‘ al-gharar) because the success of conception is not guaranteed. In the hadith narrated by Ibn ’Umar (may Allāh be pleased with them both), he said: ((نَهَى النَّبِيُّ ﷺ عَنْ عَسْبِ الفَحْلِ)) "The Prophet ﷺ forbade the fee for a stallion's mating." [Al-Bukhari and Muslim]