Riyad as-Salihin, Book 4, Hadith 797 (In-Book) ⓘ

Abu Hurairah (May Allah be pleased with him) reported: Messenger of Allah said to a man who was performing Salat while his lower garment was trailing, "Go and perform your Wudu' again." That man went and came back having performed it. The Messenger of Allah said (again), "Go and perform your Wudu'." Someone present said to Messenger of Allah: "O Messenger of Allah! You ask him to perform his Wudu' and then you kept silent (without saying the reason for it)." He said, "He performed Salat while his lower garment was below his ankels. Allah does not accept the Salat of a man who trails his lower garment."[Abu Dawud].

وعن أبى هريرة رضى الله عنه قال‏:‏ بينما رجل يصلى مسبل إزاره، قال له رسول الله صلى الله عليه وسلم‏:‏ ‏"‏اذهب فتوضأ‏"‏ فذهب فتوضأ، ثم جاء فقال ‏:‏‏"‏ اذهب فتوضأ‏"‏ فقال رجل يا رسول الله ما لك أمرته أن يتوضأ ثم سكت عنه‏؟‏ قال‏:‏ ‏"‏إنه كان يصلى وهو مسبل إزاره، وإن الله لا يقبل صلاة رجل مسبل‏"‏‏.‏