It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: The lower garment of a believer should be up to the middle of the shin, or half of the shin, or up to the ankles. Then, whatever part is below the ankles will be in Hell.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10555
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن، خ: 5787