Hadithcore
Sahih al-Bukhari, 758
sahih

Narrated Jabir bin Samura:

Sa`d said, "I used to pray with them a prayer similar to that of Allah's Messenger (the prayer of Zuhr and `Asr) reducing nothing from them. I used to prolong the first two rak`at and shorten the last two rak`at." `Umar said to Sa`d "This was what we thought about you."

حَدَّثَنَا أَبُو النُّعْمَانِ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ قَالَ سَعْدٌ كُنْتُ أُصَلِّي بِهِمْ صَلاَةَ رَسُولِ اللَّهِ صلى الله عليه وسلم صَلاَتَىِ الْعَشِيِّ لاَ أَخْرِمُ عَنْهَا، أَرْكُدُ فِي الأُولَيَيْنِ وَأَحْذِفُ فِي الأُخْرَيَيْنِ‏.‏ فَقَالَ عُمَرُ ـ رضى الله عنه ـ ذَلِكَ الظَّنُّ بِكَ‏.‏

References2 variants
In-Book Reference
Book 10, Hadith 152
USC-MSA web (English) reference
Vol. 1, Book 12, Hadith 725 (deprecated numbering scheme)