Jami` at-Tirmidhi 2285
Abu Umamah bin Sahl bin Hunaif narrated from some of the companions of the Prophet (s.a.w) that the Prophet (s.a.w) said:
"While I was sleeping I saw people presented before me, and that they were wearing shirts. Some of them (the shirts) reaching their breasts, and some of them reaching below that." He said: "Then 'Umar was presented before me and he was wearing  a shirt that was dragging." They said: "How did you interpret that O Messenger of Allah?" He said: "The religion."
حَدَّثَنَا الْحُسَيْنُ بْنُ مُحَمَّدٍ الْجُرَيْرِيُّ الْبَلْخِيُّ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، عَنْ مَعْمَرٍ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي أُمَامَةَ بْنِ سَهْلِ بْنِ حُنَيْفٍ، عَنْ بَعْضِ، أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏"‏ بَيْنَمَا أَنَا نَائِمٌ رَأَيْتُ النَّاسَ يُعْرَضُونَ عَلَىَّ وَعَلَيْهِمْ قُمُصٌ مِنْهَا مَا يَبْلُغُ الثُّدِيَّ وَمِنْهَا مَا يَبْلُغُ أَسْفَلَ مِنْ ذَلِكَ فَعُرِضَ عَلَىَّ عُمَرُ وَعَلَيْهِ قَمِيصٌ يَجُرُّهُ ‏"‏ ‏.‏ قَالُوا فَمَا أَوَّلْتَهُ يَا رَسُولَ اللَّهِ قَالَ ‏"‏ الدِّينَ ‏"‏ ‏.‏