Muhammad ibn Ali ibn Mahbub from Yaqub ibn Yazid from Ibn Abi Umayr from Hafs from Abu Abdillah عليه السلام, peace be upon him, who said:
I asked Imam al-Sadiq عليه السلام about the one who falls unconscious. Imam عليه السلام said: “He makes up the prayer of one day.”
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 3, p. 336