Sunan an-Nasai Book 13, Hadith 1312

أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا يَحْيَى بْنُ آدَمَ، قَالَ حَدَّثَنَا مَالِكٌ، - وَهُوَ ابْنُ مِغْوَلٍ - عَنْ طَلْحَةَ بْنِ مُصَرِّفٍ، عَنْ زَيْدِ بْنِ وَهْبٍ، عَنْ حُذَيْفَةَ، أَنَّهُ رَأَى رَجُلاً يُصَلِّي فَطَفَّفَ فَقَالَ لَهُ حُذَيْفَةُ مُنْذُ كَمْ تُصَلِّي هَذِهِ الصَّلاَةَ قَالَ مُنْذُ أَرْبَعِينَ عَامًا ‏.‏ قَالَ مَا صَلَّيْتُ مُنْذُ أَرْبَعِينَ سَنَةً وَلَوْ مِتَّ وَأَنْتَ تُصَلِّي هَذِهِ الصَّلاَةَ لَمِتَّ عَلَى غَيْرِ فِطْرَةِ مُحَمَّدٍ صلى الله عليه وسلم ثُمَّ قَالَ إِنَّ الرَّجُلَ لَيُخَفِّفُ وَيُتِمُّ وَيُحْسِنُ ‏.‏

It was narrated from Hudhaifah that:He saw a man praying (And his bowing and prostration) were lacking. Hudhaifah said to him: 'For how long have you been praying like this?' He said: "For forty years.' He said: 'You have not been praying for forty years and if you die praying like this, you will have died following a path other than the path of Muhammad (ﷺ). Then he said: 'It is possible for a man to pray briefly, but still do it properly