Full Sharh — Riyad as-Salihin 928
وعن ابن عباس رضي الله عنهما قال: رأى رسول الله صلى الله عليه وسلم حمارًا موسوم الوجه، فأنكر ذلك؟ فقال: والله لا أسمه إلا أقصى شيء من الوجه، وأمر بحماره، فكوي في جاعرتيه، فهو أول من كوى الجاعرتين. ((رواه مسلم)).((الجاعرتان)): ناحية الوركين حول الدبر.
English Translation
Ibn 'Abbas (May Allah be pleased with them) said:: The Messenger of Allah (ﷺ) saw an ass which had been branded on the face. He disapproved of it. Upon this Ibn 'Abbas (May Allah be pleased with them) said, "By Allah, I shall not brand (the animal) but on a part at a distance from the face." Ibn 'Abbas (May Allah be pleased with them) then commanded branding on the hips; he was the first person to brand the animals on hips..
Source
Riyad as-Salihin(رياض الصالحين)
The Book of the Prohibited actions
Hadith Number
928