Sunan at-Tirmithiy كتاب الصلاة باب ما جاء فيمن يسمع النداء فلا يجيب
'Imrān Ibn-Ḥusayn said, "I asked the Messenger of God, peace and blessings of God be upon him, about the prayer of a man [who prays] while sitting. He replied, 'Whoever prays while standing, then that is best. Whoever prays while sitting, earns half the reward of the one who stands. And whoever prays while lying down, earns half the reward of the one who sits.'" Click on ḥadīth to read more
'Imrān Ibn-Ḥusayn said, "I asked the Messenger of God, peace and blessings of God be upon him, about the prayer of the sick. He replied, 'Pray standing. If you cannot, then sitting. If you cannot, then [lying] on one side.'" Click on ḥadīth to read more