Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 537
Narrated Ibn 'Umar:
On the day of Khaibar, Allah's Apostle divided (the war booty of Khaibar) with the ratio of two shares for the horse and one-share for the foot soldier. (The sub-narrator, Nafi' explained this, saying, "If a man had a horse, he was given three shares and if he had no horse, then he was given one share.")