"I asked the Prophet ﷺ about one who prays sitting down. He said: 'Whoever prays standing up is better, and one who prays sitting down will have half the reward of one who prays standing up. And whoever prays lying down will have half the reward of one who prays sitting down.'" (Using translation from Nasāʾī 1660)  

سَأَلْتُ النَّبِيَّ ﷺ عَنِ الَّذِي يُصَلِّي قَاعِدًا فَقَالَ «مَنْ صَلَّى قَائِمًا فَهُوَ أَفْضَلُ وَمَنْ صَلَّى قَاعِدًا لَهُ نِصْفُ أَجْرِ الْقَائِمِ وَمَنْ صَلَّى نَائِمًا فَلَهُ نِصْفُ أَجْرِ الْقَاعِدِ»