The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, informed me from Ahmad ibn Muhammad, from his father Ahmad ibn Idris, from Ahmad ibn Muhammad ibn ʿIsa, from al-Husayn ibn Saʿid, from Hammad, from Shuayb, from Abu Basir, who said: I asked Abu Abdullah عليه السلام about them (rinsing the mouth and sniffing water into the nose), and Imam عليه السلام said: "They are part of ablution (Wuduʾ), but if you forget them, you do not need to repeat."