Sahih Al Bukhari (511)

عن أبي هريرة قال {أقيمت الصلاة فسوى الناس صفوفهم فخرج رسول الله صلى الله عليه وسلم فتقدم وهو جنب ثم قال على مكانكم فرجع فاغتسل ثم خرج ورأسه يقطر ماء فصلى بهم}

Abu Hurayrah (may Allah be pleased with him) narrated that once Iqamah (the call for starting Salah) was pronounced and the people had straightened the rows, Allah’s Messenger (peace be upon him) went forward (to lead the prayer) but he was Junub (in the state of major ritual impurity), so he said, “Remain in your places.” And he went out, took a bath and returned with water trickling from his head. Then he led Salah.