Sahih Bukhari
Shortening the Prayers (At-Taqseer)
Volume: 002 / Book Number: 020 / Hadith Number: 217
Narrated'Abdullah bin Buraida:
'Imran bin Husain had piles. Once Abu Ma mar narrated from 'Imran bin Husain had said, "I asked the Prophet (p.b.u.h) about the prayer of a person while sitting. He said, 'It is better for one to pray standing; and whoever prays sitting gets half the reward of that who prays while standing; and whoever prays while Lying gets half the reward of that who prays while sitting.' "