The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Ahmad ibn Muhammad, from his father, from Sa’d ibn Abdullah, from Ahmad ibn Muhammad ibn Isa, from Ahmad ibn Muhammad ibn Abi Nasr, from Abdul Karim ibn Amr, from Abdullah ibn Abi Ya’fur, from Abu Abdullah عليه السلام, who said: Imam عليه السلام said: "If you have doubt regarding anything from the ablution after you have moved on to something else, then your doubt is of no significance. Doubt only matters when you are still engaged in something and have not yet completed it."