It is narrated from Hazrat Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: The lower garment should be up to the shin or the ankles; there is no good in it being below that.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 12424
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن