Musannaf Ibn Abi Shayba 23:125

Waki’ narrated to us, he said: Sufyan narrated to us, from Abu Ishaq, from Abu Layla al-Kindi, from a servant of Hujr ibn ‘Adi, that Hujr saw a son of his come out from the privy and he did not perform ablution. He said: "O servant, hand me the scroll from the niche. I heard ‘Ali saying: 'Purification is half of faith.'"