صحيح البخاري
Sahih Bukhari
كتاب الهبة
The Book of Gifts and The Superiority of Giving Gifts and The Exhortation for Giving Gifts
باب إذا حمل رجل على فرس فهو كالعمرى والصدقة:
Chapter. If somebody gives another person a horse (as a gift) then the rule is the same as that concerning the Umra or Sadaqa (i.e., the giver has no right to claim restitution).