He said he asked the Prophet (ﷺ) about a man who prays sitting, and he replied, “If he prays standing that is more excellent; but one who prays sitting has half the reward of one who stands, and one who prays lying down has half the reward of one who sits.” Bukhari transmitted it.

وَعَن عمرَان بن حُصَيْن: أَنَّهُ سَأَلَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْ صَلَاةِ الرَّجُلِ قَاعِدًا. قَالَ: «إِنْ صَلَّى قَائِمًا فَهُوَ أَفْضَلُ وَمَنْ صَلَّى قَاعِدًا فَلَهُ نِصْفُ أَجْرِ الْقَائِمِ وَمَنْ صَلَّى نَائِمًا فَلَهُ نصف أجل الْقَاعِد» . رَوَاهُ البُخَارِيّ