I was sleeping and I did not hear the adhaan of Fajr, and the alarm clock was running slow. After I had drunk a cup of water the iqaamah for prayer was given. What should I do? Please advise me, may Allaah reward you.


Praise be to Allaah.
 

The correct scholarly view is that whoever eats thinking that
Fajr (dawn) has not yet come, then finds out that it had in fact come, does
not have to do anything, because he was unaware of the time, so he is
excused. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: If
a fasting person eats or drinks anything that breaks the fast out of
ignorance, then his fast is still valid, whether he was unaware of the time,
or unaware of the ruling, such as a man who gets up at the end of the night,
and thinks that dawn has not yet come, so he eats and drinks, then he finds
out that dawn had in fact come – his fast is still valid because he was
unaware of the time. An example of one who is not aware of the ruling is a
fasting person who has cupping done and does not know that cupping
invalidates the fast, so we say to him: your fast is still valid. The
evidence for that is the words of Allaah (interpretation of the meaning): 

“Our Lord! Punish us not if we forget or fall into error,
our Lord! Lay not on us a burden like that which You did lay on those before
us (Jews and Christians); our Lord! Put not on us a burden greater than we
have strength to bear. Pardon us and grant us forgiveness. Have mercy on us.
You are our Mawlaa (Patron, Supporter and Protector) and give us victory
over the disbelieving people”

[al-Baqarah 2:286] 

That is the evidence from the Qur’aan. The evidence from the
Sunnah is the hadeeth of Asma’ bint Abi Bakr (may Allaah be pleased with
her) which was narrated by al-Bukhaari in his Saheeh. She said: “We
broke our fast on a cloudy day at the time of the Messenger of Allaah
(peace and blessings of Allaah be upon him), then the sun came out.” That
meant that they had broken their fast during the day, but they did not
realize, because they thought that the sun had set. But the Prophet
(peace and blessings of Allaah be upon him) did not tell them to make up
that day; if it had been obligatory to make it up he would have told them to
do so. And if he had told them to do that it would have been transmitted to
us. 

Majmoo’ al-Fataawa, 19. 

See also question no. 38543.