All eyes will be on the sky tonight, searching for the crescent, it is forbidden to fast on the assumption that tomorrow fasting may begin, you have to make sure you are well informed, if you sleep on the assumption of fasting tomorrow then you have disobeyed the Prophet {Peace be upon him}.



Proof:-----------


Narrated that ‘Ammaar ibn Yaasir (may Allaah be pleased with him) said: “Whoever fasts on the day concerning which there is doubt has disobeyed Abu’l-Qaasim (peace and blessings of Allaah be upon him).”

Al-Tirmidhi (686) and al-Nasaa’i (2188)




Al-Haafiz said in Fath al-Baari: 

It was understood from this that it is haraam to fast the day of doubt, because the Sahaabah would not say such a thing based on personal opinion.  

The day of doubt is the thirtieth (30th) of Sha’baan if the new moon cannot be seen because of clouds etc. It is called the day of doubt because it could be the thirtieth of Sha’baan, or it could be the first day of Ramadaan. It is haraam to fast on this day, unless it coincides with a day on which a person habitually fasts. 



Al-Nawawi said in al-Majmoo’ (6/400) concerning the ruling on fasting the day of doubt: 

If a person observes a voluntary fast on this day, and he has a reason for doing so, such as having the habit of fasting every day, or of fasting alternate days, or fasting on particular days such as Mondays, and it happens to coincide with that day, then it is permissible for him to fast on this day; there is no difference of opinion among our companions regarding that. The evidence for that is the hadeeth of Abu Hurayrah: “Do not anticipate Ramadaan by fasting one or two days before it begins, but if a man habitually fasts, then let him fast.” If he does not have a reason, then it is haraam for him to fast on this day. 

al-Majmoo’ (6/400).

if you have no intention of fasting till in the morning and you were informed that fasting had already began because last night the moon was sighted then you are expected to abstain from eating and drinking but after ramadan you will make it up because you have missed the first Ramadan, NO INTENTION means NO RAMADAN.

Saying Nawaitul bla bla bla is Bid'a (innovation), abstain from innovation, intention occurs in the heart, if you intend to do something then you have done the intention, samething with ablution, salat etc. It is not uttered. There is no evidence of any of them in the hadith.

If you wake up for sahur or Sari or suhur then automatically you have make the intention but if you wake up after dawn (once fajr prayer enters) then you don't have that fasting. If you have confirmed in the night that tomorrow is Ramadan and prepared to partake it then even if you skip Sahur or sari or suhur whichever way you may call it, then you don't need to worry because you have done the intention right from the night.



From the Prophet (blessings and peace of Allah be upon him), according to which he said: “Whoever does not decide to fast before dawn, his fast does not count.”
Narrated by at-Tirmidhi (730) and classed as saheeh by al-Albaani in Saheeh at-Tirmidhi.


At-Tirmidhi said, after quoting this hadith: What this means, according to the scholars, is that there is no fast for the one who does not decide to fast before dawn breaks, whether in Ramadan or when making up missed Ramadan fasts or when fasting in fulfilment of a vow. If he does not form the intention from the night before, then it does not count. As for voluntary fasts, it is permissible for him to form the intention after he gets up (in the morning). This is the view of ash-Shaafa‘i, Ahmad and Is-haaq. End quote. 

The first intention is expected to cover all the 29 or 30 days of Ramadan meaning you won't be repeating the intention for all the 29 or 30 days, once is sufficient for all