Sahih Bukhari Volume 1, Book 4, Hadith Number 239

Narated By Abu Huraira : Allah’s Apostle said, “We (Muslims) are the last (people to come in the world) but (will be) the foremost (on the Day of Resurrection).” The same narrator told that the Prophet had said, “You should not pass urine in stagnant water which is not flowing then (you may need to) wash in it.”