Safwan ibn Yahya narrated from Al-'Is ibn al-Qasim, who said: "I asked Abu Abdullah عليه السلام about a group of people who converted to Islam during the Month of Ramadan after some days had passed. Are they required to fast the days that have passed, or the day they embraced Islam? Imam عليه السلام said: 'They are not required to make up the missed days or to fast on the day they embraced Islam, unless they embraced Islam before the break of dawn on that day.'"