Sayyiduna Imran bin Husain (may Allah be pleased with him) narrates that I asked the Messenger of Allah (peace and blessings of Allah be upon him) about a man praying while sitting, so the Messenger of Allah (peace and blessings of Allah be upon him) said: "Praying while standing is superior, and the reward of the one who prays while sitting is half of the reward of the one who prays while standing."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب صلاة التطوع قاعدا / 1236