Ayyub ibn Nuh, from Safwan, from Sa’ad ibn Abi Khalaf, who said: Ghiyath narrated to me, from Abu Abdillah عليه السلام, peace be upon him:
Imam عليه السلام said: “There is no harm in the fasting person swallowing his phlegm (nukhamah).”
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 4, p. 404