Surah Yunus, Ayat 72-73

Ayat 72. "But if you turn away [from accepting my doctrine of Islamic Monotheism, i.e. to worship none but Allah], then no reward have I asked of you, my reward is only from Allah, and I have been commanded to be one of the Muslims (those who submit to Allah's Will)."

Ayat 73. They denied him, but We delivered him, and those with him in the ship, and We made them generations replacing one after another, while We drowned those who belied Our Ayat (proofs, evidences, lessons, signs, revelations, etc.). Then see what was the end of those who were warned.

Hazrat Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah  [SAWW](PBUH) said, "Do not observe Saum (fasting) for a day or two days preceding Ramadan. However, if a person is in the habit of observing Saum on a particular day (which may fall on these dates), he may fast on that day.'' [Muslim Book 6, Hadith Number 2382].

Lesson : as mentioned above in Surah Yunus Ayat 72. "I have been commanded to be one of the Muslims" "However, if a person is in the habit of observing Saum on a particular day'' means that if it is his routine to observe Saum on these days, then he can do so two days before the advent of Ramadan. The reason being that in that case his Saum will not be for the reception of Ramadan but a matter of routine. Some people have taken "one or two days before'' to mean the first two days of the second half of Shawwal on the grounds that some Ahadith contain prohibition of observing Saum in the second fortnight of Shawwal. Because of this injunction, it is not permissible to observe Saum in these days, except in case it is one's routine.