Riyad as-Salihin

Ibn 'Umar (May Allah be pleased with them) reported: My lower garment was trailing as I passed by the Messenger of Allah (ﷺ) so he said, "Raise your lower garment, Abdullah." I lifted it up and he told me to raise it higher. I complied with his orders and as I was still trying to find the best place (for it), one of the people asked where it should reach and he (ﷺ) replied, "Half way down the knees."

[Muslim].