Sayyiduna Anas bin Malik (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "The example of the five prayers is like a river of clear water that passes by a person's door, and he bathes in it five times every day; then no dirt remains on him."
Abu Ya'la and al-Bazzar recorded it. Its chain contains a narrator, Dawud bin al-Zibriqan, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1652