Sunan an-Nasa'i, Volume 2, Book 11, Hadith 1003 (DarusSalam) ⓘ
Abu 'Awn said: "I heard Jabir bin Samurah say: 'Umar said to Sa'eed': "The people are complaining about everything about you, even about your prayer." Sa'd said: "I take my time in the first two rak'ahs and I make the other two shorter. I do my best to follow the example of the Messenger of Allah in prayer." 'Umar said: 'That is what I thought about you.'"
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنِي أَبُو عَوْنٍ، قَالَ سَمِعْتُ جَابِرَ بْنَ سَمُرَةَ، يَقُولُ قَالَ عُمَرُ لِسَعْدٍ قَدْ شَكَاكَ النَّاسُ فِي كُلِّ شَىْءٍ حَتَّى فِي الصَّلاَةِ . فَقَالَ سَعْدٌ أَتَّئِدُ فِي الأُولَيَيْنِ وَأَحْذِفُ فِي الأُخْرَيَيْنِ وَمَا آلُو مَا اقْتَدَيْتُ بِهِ مِنْ صَلاَةِ رَسُولِ اللَّهِ صلى الله عليه وسلم . قَالَ ذَاكَ الظَّنُّ بِكَ .
also referenced under: Hadith 1002 (Reference) & Book 11, Hadith 127 (In-Book)