Musnad Ahmad 1015:17

Surayj ibn al-Nu‘man narrated to us, Abu Ishaq Yahya ibn Maymun—meaning al-‘Attar—narrated to us, Yahya ibn Abi Kathir narrated to me, Zayd ibn Salam narrated to me, from Abu Salam, that ‘Abd al-Rahman al-Ash‘ari narrated to him, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Purity is half of faith." He then mentioned the like of it, except that he said: "Prayer is a proof, and charity is a light."