Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: I passed by the Messenger of Allah (peace and blessings be upon him) and my lower garment (izar) was hanging down. He said: "O Abdullah, raise your lower garment." I raised it, and he said: "Higher." So I raised it higher, and after that I always kept striving (to keep it so). Some people asked: Up to where? He said: To the middle of the shins.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3316
Ala' bin Abd al-Rahman narrates from his father: I asked Abu Sa'id al-Khudri (may Allah be pleased with him) about the lower garment (izar), and he said: I will tell you what I heard from the Messenger of Allah (peace and blessings be upon him): "The lower garment of the believer reaches the middle of the shins. There is no harm in keeping it down to the ankles, but whatever is below the ankles will burn in Hell. And Allah Almighty will not look (with mercy, on the Day of Resurrection) at the one who lets his lower garment trail out of arrogance and pride."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3317
Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Whatever part (of the body) is covered by the lower garment below the ankles will burn in the Fire." These are the words of Adam's narration; the words of Abd al-Samad's narration are: "Whatever of the lower garment is below the ankles will burn in the Fire."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3318
Yazid bin Abi Sumayyah narrates: I heard Sayyiduna Ibn Umar (may Allah be pleased with them both) say: Whatever the Messenger of Allah (peace and blessings be upon him) said about the lower garment (izar) applies to the shirt as well.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3319