بسم الله الرحمن الرحيم
Imām Ibn Kathīr said:
The Prophet (ﷺ) said,
«إِنَّا أُمَّةٌ أُمِّيَّةٌ لَا نَكْتُبُ وَلَا نَحْسِبُ، الشَّهْرُ هكَذَا وَهكَذَا وَهكَذَا»
We are an Ummi nation, neither writing nor calculating. The (lunar) month is like this, this and this (i.e. thirty or twenty-nine days).
(Musnad Imām Ahmad 5017, 5137. And al-Fath of Ibn Hajr 4/108-109)
This Hadīth states that Muslims do not need to rely on books, or calculations to decide the timings of their acts of worship.
(Umdatul-Tafsīr 1/128)
Shaykh Sālih al-Fawzān said:
It is not permissible to calculate the beginning of the fasting by depending upon astronomical calculations. This is not prescribed by Allāh and was not legislated by the prophet (ﷺ). Rather he linked the start of fasting with the sighting of the new moon, saying “Fast when it is sighted and end the fast when it is sighted” (al-Bukhārī 3/34).
Fasting (in the month of ramadān) commences when two conditions are present: When the new moon is sighted or when thirty days of Sha’bān have passed.
Astronomical calculations are not permissible with regards to fasting as it is a human invention which may err sometimes and be accurate at other times.
The prophet (ﷺ) did not command us to depend on it to determine the beginning or fasting in the month of ramadān. Instead, he ordered us to sight the crescent moon. The method of sighting is a visual one – by direct eyesight or by the use of telescopes and other such equipment. The use of such tools does not transform the nature of the method to something other than sighting. They are means to aid the sighting.
(Abridged, Sharh Zād al-Mustaqnī’ pg. 578)
Imām ibn Abdul-Barr said:
What the majority of scholars agree with is that Ramadān should not be fasted except with certainty that Sha’bān has ended, and certainty in (establishing) that; is the sighting of the crescent or the completion of thirty days of Sha’bān. And similarly, the end of Ramadān is not decided upon except with similar certainty.
Allāh said: ‘So whoever of you sights the month, then he must fast it‘ (Al-Baqarah:185)
He means, and Allāh knows best, whoever among you knows with certainty that the month has begun, let him fast it, and the knowledge with certainty is the true sighting.
(Al-Istidhkār 3/276)
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