Narrated by al-Husayn ibn Sa’id from Fadalah ibn Ayyub from al-’Alaʾ ibn Razin from Muhammad ibn Muslim, who said:
I said to Abu Abdillah عليه السلام: "A man prayed Fajr when the dawn appeared." Imam عليه السلام said: "There is no problem."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 2, p. 38