وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ هِلاَلِ بْنِ يَسَافٍ، عَنْ أَبِي يَحْيَى، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ حُدِّثْتُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ صَلاَةُ الرَّجُلِ قَاعِدًا نِصْفُ الصَّلاَةِ ‏"‏ ‏.‏ قَالَ فَأَتَيْتُهُ فَوَجَدْتُهُ يُصَلِّي جَالِسًا فَوَضَعْتُ يَدِي عَلَى رَأْسِهِ فَقَالَ مَا لَكَ يَا عَبْدَ اللَّهِ بْنَ عَمْرٍو قُلْتُ حُدِّثْتُ يَا رَسُولَ اللَّهِ أَنَّكَ قُلْتَ ‏"‏ صَلاَةُ الرَّجُلِ قَاعِدًا عَلَى نِصْفِ الصَّلاَةِ ‏"‏ ‏.‏ وَأَنْتَ تُصَلِّي قَاعِدًا قَالَ ‏"‏ أَجَلْ وَلَكِنِّي لَسْتُ كَأَحَدٍ مِنْكُمْ ‏"‏ ‏.‏

'Abdullah b. 'Amr reported: It was narrated to me that the Messenger of Allah (PBUH) had said: The prayer observed by a person sitting is half of the prayer. I came to him (PBUH) and found him praying in a sitting position. I placed my hand on his head. He said: O 'Abdullah b. 'Amr, what is the matter with you? I said: Messenger of Allah, it has been narrated to me that you said: The prayer of a man in a sitting position is half of the prayer, whereas you are observing prayer sitting. He (the Holy Prophet) said: Yes, it is so, but I am not like anyone amongst you. Translation Not Available

Book Ref: Sahih Muslim Book 6 Hadith 1600
Web Ref:  Sahih Muslim Book 4 Hadith 735 a