Musannaf Ibn Abi Shayba 1:97

97. Abd al-Rahim ibn Sulayman narrated to us, from Wasil ibn al-Sa’ib, from Abu Surah, from his paternal uncle Abu Ayyub, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Excellent are those who perform *takhlil* (interlacing/cleansing): that you perform *takhlil* between your fingers with water, and that you perform *takhlil* of the food [from between your teeth]."