Musannaf Ibn Abi Shayba 3:6359

Abu Usama narrated to us, from Isma'il, who said: Bayan narrated to us, from Hakim ibn Jabir, who said: Hudhayfah said: "Indeed, among the most proficient of people in recitation is a hypocrite who does not leave out a 'waw' nor an 'alif', twisting it with his tongue just as a cow twists the lush grass with its tongue; it does not pass beyond his collarbone."