The Case of One Who Wakes up in the Morning with an Intention to Fast, but Who Does Not Do So or Vice Versa when Fasting Is a Compensatory Fast for the Missed Fast in the Month of Ramadan or Other Days

3. Ahmad ibn Muhammad from has narrated from al-‘Abbas ibn Ma‘ruf from Safwan ibn Yahya from ibn Sinan from ‘Ammar ibn Marwan from Sama‘ah ibn Mehran, from abu ‘Abdillah عليه السلام regarding his saying, ‘A fasting person has the choice until Zawal (declining of the sun toward the west at noontime)’. He said: ‘It is about the obligatory (fast). In the case of the optional (fast), one has the choice to stop fasting any time up to sunset.’”