Ali ibn al-Hasan, from Ali ibn Asbat, from Ala ibn Razin, from Muhammad ibn Muslim, who said:
I (narrator) asked Abu Abdillah عليه السلام, peace be upon him, about ‘regurgitation (al-qals), does it break the fast of the fasting person?’ Imam عليه السلام said: “No.”
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 4, p. 335