Allaah, may He be exalted, says (interpretation of the meaning):
“It is made lawful for you to have sexual relations with your wives on the night of As‑Sawm (the fasts). They are Libaas [i.e. body-cover, or screen, or Sakan (i.e. you enjoy the pleasure of living with them)] for you and you are the same for them. Allaah knows that you used to deceive yourselves, so He turned to you (accepted your repentance) and forgave you. So now have sexual relations with them and seek that which Allaah has ordained for you (offspring), and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night), then complete your Sawm (fast) till the nightfall”
What this means is that Allaah has allowed those who are fasting to eat and drink at night until he is certain that dawn has come. What is meant by the white thread is the day, and the black thread is the night.
Al-Haafiz said: What the verse means is until the whiteness of day can be distinguished from the blackness of night. This happens when the true dawn appears.
The words “of dawn” serve to explain what is meant by “the white thread” and there is no need to explain what is meant by the black thread because explaining the one makes it clear what is meant by the other. End quote.
Some of the Sahaabah (may Allaah be pleased with them) understood the verse in a manner other than what it means. They thought that what was meant was a thread in the real sense. One of them would put two threads, one white and one black, beneath his pillow or tie them to his foot, and he would carry on eating until he could tell them apart. They misunderstood it because at first Allaah revealed the verse without the words “of dawn”, then after a while (some scholars say that it was after a year), Allaah revealed the verse with the words “of dawn”. Then they realized that what was meant by the white thread was the light of dawn (the day) and what was meant by the black thread was night.
Al-Bukhaari (1917) and Muslim (1091) narrated that Sahl ibn Sa’d said: The verse “and eat and drink until the white thread appears to you distinct from the black thread” [al-Baqarah 2:187] was revealed, and the words “of dawn” were not revealed. When people wanted to fast, one of them would tie a white thread and a black thread to his foot, then he would carry on eating until he could tell them apart when he looked at them. Then after that Allaah revealed the words, “of dawn,” then they realized that what was meant by that was night and day.
The Sahaabah interpreted the word thread according to its apparent meaning, as they understood it, then when the words “of dawn” were revealed, they understood what was meant.
Al-Bukhaari (1916) narrated that ‘Adiyy ibn Haatim (may Allaah be pleased with him) said: “When the words ‘until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night)’ [al-Baqarah 2:187 – interpretation of the meaning] were revealed, I took a black rope and a white rope and put them beneath my pillow, and I started to look at them during the night, but I could not see any distinction between them. The next morning I went to the Messenger of Allaah (peace and blessings of Allaah be upon him) and told him about that. He said, ‘Rather that is the blackness of the night and the whiteness of the day.’”
According to a report narrated by al-Bukhaari (4510) he said: “You must be huge.” According to another report (4509) he said: “Your pillow must be very wide, if the white thread and the black thread are beneath your pillow.” And according to another report: (4510) “The back of your head must be very wide.”
The story of ‘Adiyy ibn Haatim occurred after Allaah had revealed the words “of dawn”, i.e., after the hadeeth of Sahl quoted above. Some of the scholars explained Adiyy’s mistake of misunderstanding the verse even though the words “of dawn” had been revealed, by noting that the hadeeth of Sahl had not reached ‘Adiyy’, or that in the dialect of his people the words “white thread” and “black thread” were not used to refer to day and night.
Hence Ibn Hibbaan commented on the hadeeth of ‘Adiyy by noting that “the language of the Arabs varies,” and pointed out that in the language of ‘Adiyy, the darkness of night and the light of day were not described as a black thread and white thread. Al-Qurtubi said: The hadeeth of ‘Adiyy is later than the hadeeth of Sahl. It is as if ‘Adiyy had not heard what was said in the hadeeth of Sahl, rather he only heard the verse and understood it as it sounded to him. End quote.
Al-Haafiz said: As for ‘Adiyy, it is as if in the language of his people they did not refer to the dawn as a thread, or he forgot the words “of dawn” until the Prophet (peace and blessings of Allaah be upon him) reminded him of that.
Al-Nawawi said, following al-Qaadi ‘Iyaad: Rather the black and white threads were interpreted according to their apparent meaning by some Bedouin who did not have much knowledge, such as the men from whom Sahl narrated, and some of those in whose dialect the dawn was not referred to as a thread, such as ‘Adiyy. End quote.
With regard to the words of the Prophet (peace and blessings of Allaah be upon him), “The back of your head must be very wide,” some of them claimed that what the Prophet (peace and blessings of Allaah be upon him) meant by that was that he was unintelligent. They claimed that if the back of the head is wide, this is a sign of stupidity, and they wrote poetry about that. But many of the scholars rejected this, such as al-Qurtubi, al-Qaadi ‘Iyaad and al-Nawawi.
Some people interpreted this as a criticism of him for that misunderstanding. It is as if they understood it as an accusation of ignorance and lack of understanding, but it is not as they say. Rather he meant – and Allaah knows best – if your pillow covers the two threads to which Allaah referred then it must be wide indeed. Hence immediately after that he said: “Rather that is the blackness of the night and the whiteness of the day.” It is as if he said: How can they fit under your pillow? And the words “The back of your head must be very wide” mean that the pillow which covers the night and day cannot be rested upon except by a head that is very wide. End quote.
Al-Qaadi said: What this means is that if you put under your pillow the two threads that Allaah meant, namely the night and day, and your pillow covered them, then it must be very wide. This is what is meant in the other report narrated in Saheeh al-Bukhaari – “The back of your head must be very wide” – and in the other report: “You must be huge.”
See: Fath al-Baari, commentary on hadeeth no. 1917 and 1916’ Sharh Muslim by al-Nawawi, hadeeth no. 1090, 1091
Among the rulings that are derived from this verse is the ruling that if a person is unsure whether dawn has broken, he may carry on eating and drinking until he is sure of it, because Allaah says “until the white thread (light) of dawn appears to you distinct from the black thread”.
‘Abd al-Razzaaq narrated that Ibn ‘Abbaas said: Allaah has permitted you to eat and drink so long as you are not sure. Al-Haafiz said: its isnaad is saheeh.
Ibn Abi Shaybah narrated that Abu’l-Duha said: A man asked Ibn ‘Abbaas about sahoor and Ibn ‘Abbaas said: Eat so long as you are uncertain, until you are no longer uncertain. This is the view of the majority of scholars.
Shaykh Ibn ‘Uthaymeen said in al-Sharh al-Mumti’ (6/247):
If a person is not fasting, and he is not sure whether dawn has broken, his fast is valid, because Allaah says (interpretation of the meaning):
“So now have sexual relations with them and seek that which Allaah has ordained for you (offspring), and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night), then complete your Sawm (fast) till the nightfall”
The opposite of certainty is uncertainty and doubt; so long as we are not certain, we may eat and drink. This issue falls into five categories:
1-If he is certain that dawn has not come, such as if dawn comes at five o’clock and he eats and drinks at four-thirty, his fast is valid.
2-If he is certain that dawn has come, such as if he eats at five-thirty, then his fast is invalid.
3-If he eats and he is unsure whether dawn has come or not, but he thinks it most likely that it has not come, then his fast is valid.
4-If he eats and drinks, and he thinks it most likely that dawn has come, then his fast is valid.
5-If he eats and drinks and is unsure, then his fast is valid. End quote.
And Allaah knows best.