Musannaf Ibn Abi Shayba 16:855

Abu Bakr narrated to us, he said: Malik narrated to us, he said: Zuhayr narrated to us, he said: Umarah ibn Ghaziyyah narrated to us, from Abd al-Rahman ibn al-Qasim. Zuhayr said: Umarah believes it is from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, good or beautiful hair is from the clothing of Allah, so honor it." He used to dislike removing it. Zuhayr claimed that it is the *nas'a* (whiteness/purity).