It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was asked about praying while sitting, and he (peace and blessings be upon him) said: "Praying standing is more virtuous; one who prays sitting receives half the reward of one who prays standing, and one who prays lying down receives half the reward of one who prays sitting."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3680