Ibn 'Umar reported: I happened to pass before Allah's Messenger (may peace be upon bin) with my lower garment trailing (upon the ground). He said: 'Abdullah, tug up your lower garment,, I tugged it up, and he again said: Tug it still further, and I tugged it still further and I went on tugging it afterward, whereupon some of the people said: To what extent? Thereupon he said: To the middle of the shanks.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي أَبُو الطَّاهِرِ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي عُمَرُ بْنُ مُحَمَّدٍ، عَنْ عَبْدِ اللَّهِ بْنِ، وَاقِدٍ عَنِ ابْنِ عُمَرَ، قَالَ مَرَرْتُ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم وَفِي إِزَارِي اسْتِرْخَاءٌ فَقَالَ " يَا عَبْدَ اللَّهِ ارْفَعْ إِزَارَكَ " . فَرَفَعْتُهُ ثُمَّ قَالَ " زِدْ " . فَزِدْتُ فَمَا زِلْتُ أَتَحَرَّاهَا بَعْدُ . فَقَالَ بَعْضُ الْقَوْمِ إِلَى أَيْنَ فَقَالَ أَنْصَافِ السَّاقَيْنِ .
sunnah.com