Fasting begins with Sahri and ends with Iftar. Taking food and drink in the last part of night is Sahri and breaking fast with light food and drink is Iftar.
Having a required meal before Subhe Sadeq is Sunnah-e-Nabawi. Sahri
is very important. Rasulullah (Sm) said, “The difference between us and Ahle Kitab is that we take the meal of Sahri, but they don’t.”
He said, “Take the meal of Sahri, because in it lies abundance.” (Bukhari Sharif, Muslim Sharif)
So, if one has no hunger even, a glass of water may be taken as Sunnat.
The time for Sahri is described in the Holy Quran: ” … So now associate with them and seek what God hath ordained for you, and eat and drink, until the white thread of dawn appear to you distinct from its black thread; then complete your fast till the night appears ….” (Sura Baqara 2:187)
Allama Yusuf Ali in the ‘Holy Quran: Translation and Commentary’ explains the time of ‘true dawn’, after which the fast begins : “Those in touch with Nature know the beautiful effects of early dawn.
First appear thin white indefinable streaks of light in the east; then a dark zone supervenes; followed by a beautiful pinkish white zone clearly defined from the dark. This is true dawn ; after that the fast begins.”
The Hadith described by Hazrat Zayed bin Sabit (Ra) is quoted here to have clear conception about the time of Sahri. He said, “We took our Sahri with Rasulullah (Sm) and then stood for Fazar prayer.” He was asked: “How far was the gap in between the both — the Sahri and the Fazar prayer?” He replied: The time in between was as long as required to recite 50 Ayats of the Holy Quran.”
So, it is clear that the time for meal of Sahri ends with the appearance of Subhe Sadeq. Completing Sahri should not depend on the Azan of Fazar; but it should be completed before Subhe Sadeq.
For easy and smooth keeping of fasting, Rasulullah (Sm) stressed on having required meal at Sahri.
