Fast When You See It!
“Fast when you see it (the new moon) and break your fast when you see it.”
Narrated by al-Bukhaari, 1909; Muslim, 1081.
On the authority of the mother of the faithful, Aaishah (may Allah be pleased with her), who said: The Messenger of Allah (peace and blessings of Allah be upon him) said,
“He who introduces something in this matter of ours [i.e., Islam] that is not of it, will have it rejected [by Allah].”
Related by al-Bukhari and Muslim. In one version by Muslim it reads:
“He who does an act which we have not commanded, will have it rejected [by Allah].”
"So whoever turns away from my Sunnah (i.e., my way) is not from me.” [Al-Bukhaari & Muslim]
And whoever contends with the Messenger after the guidance has been made clear to him, and he follows a path other than the path of The Believers (The companions), We shall leave him in the path he has chosen and land him in Hellfire, what an evil refuge. (Soorah Nisa, 4:115)
But no, by your Lord, they can have no Faith, until they make you (O Muhammad SAW) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission. (An-Nisa 4:65)
The only saying of the faithful believers, when they are called to Allâh (His Words, the Qur'ân) and His Messenger (SAW), to judge between them, is that they say: "We hear and we obey." And such are the prosperous ones (who will live forever in Paradise). (An-Nur 24:51)
(And) if you differ in anything amongst yourselves, refer it to Allâh (The Quran) and His Messenger (SAW) (The Sunnah), if you believe in Allâh and in the Last Day. That is better and more suitable for final determination. (An-Nisa 4:59)
And let those who oppose the Messenger's (Muhammad SAW) commandment (i.e. his Sunnah legal ways, orders, acts of worship, statements, etc.) (among the sects) beware, lest some Fitnah (disbelief, trials, afflictions, earthquakes, killing, overpowered by a tyrant, etc.) befall them or a painful torment be inflicted on them. (An-Nur 24:63)