✅Answer: Please pay attention to the following narrations:

1 محمد بن شهاب الزُّهْرِيِّ قال سَمِعْتُ عَلِيَّ بْنَ الْحُسَيْنِ يَقُولُ يَوْمُ الشَّكِّ أَمَرْنَا بِصِيَامِهِ وَ نَهَيْنَا عَنْهُ أَمَرْنَا أَنْ يَصُومَهُ الْإِنْسَانُ عَلَى أَنَّهُ مِنْ شَعْبَانَ وَ نَهَيْنَا عَنْ أَنْ يَصُومَهُ عَلَى أَنَّهُ مِنْ شَهْرِ رَمَضَانَ و هُوَ لَمْ يَرَ الْهِلَال

📚 Al-Tahdheeb, vol. 4, p. 164

Zuhri said: 'I heard Imam Sajjad, peace and blessings of Allah be upon him, saying: 'We command and prohibit fasting the 'Day of Doubt'! We command a person to fast it as part of the month of Sha'ban, and we prohibit him from fasting it as part of the month of Ramadan while he has not sighted the crescent (of Ramadan)!'

2️⃣ From Abi Khalid al-Wasiti, he said: 'We entered upon Abu Ja'far (Imam Baqir) on a day that was doubtful as being the first of Ramadan, and his dining cloth was spread, and he was eating! And we intended to ask him (about this matter). So the Imam said: 'Come forward! Have breakfast!''

When the situation is like today and proof and witness for the sighting of the crescent have not come to you, do not fast (as part of the month of Ramadan)!... Until he said: 'Imam Ali, peace and blessings of Allah be upon him, said: 'We fasted the month of Ramadan with the Messenger of Allah, peace be upon him and his family, for 29 days, and we did not make up that (one day), and the Messenger of Allah, peace be upon him and his family, considered it complete and perfect (despite the 29 days of fasting).' And Imam Ali, peace and blessings of Allah be upon him, said: 'The Messenger of Allah, peace be upon him and his family, said: 'Whoever intentionally adds a day from another month to the month of Ramadan is not a believer in Allah and in me!'

📚 Al-Tahdheeb, vol. 4, p. 161

📚 Al-Faqih, vol. 2, p. 126

3 كان أَميرالْمُؤْمِنينَ يَقُولُ لَأَنْ أُفْطِرَ يَوْماً مِنْ شَهْرِ رَمَضَانَ أَحَبُّ إِلَيَّ مِنْ أَنْ أَصُومَ يَوْماً مِنْ شَعْبَانَ أَزِيدُهُ في شَهْرِ رَمَضَان

Sheikh Saduq said: 'The Commander of the Faithful, peace and blessings of Allah be upon him, used to say: 'If I were to break my fast on a day of Ramadan, it would be more beloved to me than to fast a day of Sha'ban and add it to Ramadan!'

4️⃣ From Sahl ibn Sa'd, he said: 'I heard Imam Reza, peace and blessings of Allah be upon him, saying: 'Fasting is based on sighting, and breaking the fast is based on sighting, and he is not from us who fasts before the sighting as a result of sighting, and breaks the fast before the sighting as a result of sighting!'

He said: 'I said to him: 'O son of the Messenger of Allah, what do you think about fasting the 'Day of Doubt'?' The Imam said: 'My father narrated to me from my grandfather from his fathers that the Commander of the Faithful, peace and blessings of Allah be upon him, said: 'That I fast a day from the month of Sha'ban is more beloved to me than that I break my fast on a day of the month of Ramadan!'

📚 Al-Faqih, vol. 2, p. 128

5️⃣ Imam Sadiq, peace and blessings of Allah be upon him, said: 'In the book of the Commander of the Faithful, peace and blessings of Allah be upon him, it is written: 'Fast (Ramadan) with the sighting of its crescent and break the fast with its sighting, and avoid doubt and assumption in this matter, and if (the beginning or end of Ramadan) is hidden from you, then complete the previous month as 30 days!'

📚 Al-Tahdheeb, vol. 4, p. 158

✅ Based on the above narrations and others, it is never permissible to consider a day as the beginning of Ramadan and fast as such without the sighting of the crescent or the passing of 30 days from the month of Sha'ban. And whoever considers a day as part of Ramadan without these two criteria is not from the Ahl al-Bayt, peace be upon them, and whoever intentionally adds a day to the beginning of Ramadan is not a believer in Allah and the Messenger of Allah, peace be upon him and his family, and the sin of this is greater than breaking the fast on a day of Ramadan!

Therefore, until the crescent of Ramadan has been sighted or 30 days have passed from the month of Sha'ban, we are only commanded to fast as part of the month of Sha'ban, and for Eid al-Fitr, we cannot break our fast except by sighting the crescent or the passing of 30 days from the month of Ramadan.

اللَّهُمَّ نَجِّنَا مِنْ مُضِّلَاتِ الْفِتَنْ!