Sunnah.com reference : Book 2, Hadith 227English translation : Book 2, Hadith 327Arabic reference : Book 2, Hadith 331
Narrated Abu Hurairah (RA):
The Prophet (ﷺ) led us in two Rak'at of one of the two, Zuhr or 'Asr prayers, and said the Taslim (salutation). He then got up and went towards a piece of wood which was at the front part of the mosque and placed his hands upon it. Abu Bakr and 'Umar were among the people, but they were afraid to speak to him. Then some of the hasty type of people came out and said, "Has the Salat (prayer) been shortened?" A man whom the Prophet (ﷺ) called Dhul Yadain (the long armed) asked: "Have you forgotten, O Allah's Messenger or has the prayer been shortened?" He said, "I have neither forgotten nor has it been shortened." He said, "Indeed you have forgotten." He [the Prophet (ﷺ)] then prayed the remaining two Rak'at, then said the Taslim (salutation). He then uttered the Takbir and prostrated similar to his normal prostration or longer, then raised up his head and uttered the Takbir. He then prostrated and uttered the Takbir, and the prostration was similar to his normal prostration or longer. He then raised his head and uttered the Takbir.

[Agreed upon, and it is al-Bukhari's wording].
وَعَنْ أَبِي هُرَيْرَةَ ‏-رَضِيَ اَللَّهُ تَعَالَى عَنْهُ‏- قَالَ : { صَلَّى اَلنَّبِيُّ ‏- صلى الله عليه وسلم ‏-إِحْدَى صَلَاتِي اَلْعَشِيّ ِ  1‏ رَكْعَتَيْنِ , ثُمَّ سَلَّمَ , ثُمَّ قَامَ إِلَى خَشَبَةٍ فِي مُقَدَّمِ اَلْمَسْجِدِ , فَوَضَعَ يَدَهُ عَلَيْهَا , وَفِي اَلْقَوْمِ أَبُو بَكْرٍ وَعُمَرُ , فَهَابَا أَنْ يُكَلِّمَاهُ , وَخَرَجَ سَرَعَانُ اَلنَّاسِ , فَقَالُوا : أَقُصِرَتْ .‏  2‏ الصَّلَاةُ , وَرَجُلٌ يَدْعُوهُ اَلنَّبِيُّ ‏- صلى الله عليه وسلم ‏-ذَا اَلْيَدَيْنِ , فَقَالَ : يَا رَسُولَ اَللَّهِ , أَنَسِيتَ أَمْ قُصِرَتْ ? فَقَالَ : " لَمْ أَنْسَ وَلَمْ تُقْصَرْ " فَقَالَ : بَلَى , قَدْ نَسِيتُ , فَصَلَّى رَكْعَتَيْنِ ثُمَّ سَلَّمَ , ثُمَّ كَبَّرَ , فَسَجَدَ مِثْلَ سُجُودِهِ , أَوْ أَطْوَلَ] ثُمَّ رَفَعَ رَأْسَهُ فَكَبَّرَ , ثُمَّ وَضَعَ رَأْسَهُ , فَكَبَّرَ , فَسَجَدَ مِثْلَ سُجُودِهِ , أَوْ أَطْوَلَ [ .‏  3‏ ثُمَّ رَفَعَ رَأْسَهُ وَكَبَّرَ }  مُتَّفَقٌ عَلَيْهِ , وَاللَّفْظُ لِلْبُخَارِيِّ .‏  4‏‏1 ‏- عند البخاري : قال محمد بن سيرين : وأكثر ظني أنها العصر .‏ وفي مسلم : إما الظهر وإما العصر .‏‏2 ‏- في البخاري : " أقصرت " .‏‏3 ‏- سقطت من الأصلين واستدركتها من البخاري .‏‏4 ‏- صحيح .‏ رواه البخاري ( 1229 )‏ ، ومسلم ( 573 )‏ .‏