‘Abd Allah b. Buraidah said: ‘Imran b. Hussain asked the prophet (peace be upon him) about the prayer a man offers in sitting condition. He replied: his prayer in standing condition is better than his prayer in sitting condition, and his prayer in sitting condition is half the prayer he offers in standing condition, and his prayer in lying condition is half the prayer he offers in sitting condition.
Sunan Abi Dawud, Book 2, Hadith 562