Sheikh Abdullah bin Abd al-Azhim Khalafi
1. The statute
Ramadan fasting is one of the pillars of the pillars of Islam and is also one of its obligations.
Allah Ta'ala says:
يا أيها الذين آمنوا كتب عليكم الصيام كما كتب على الذين من قبلكم لعلكم تتقون أياما معدودات فمن كان منكم مريضا أو على سفر فعدة من أيام أخر وعلى الذين يطيقونه فدية طعام مسكين فمن تطوع خيرا فهو خير له وأن تصوموا خير لكم إن كنتم تعلمون شهر رمضان الذي أنزل فيه القرآن هدى للناس وبينات من الهدى والفرقان فمن شهد منكم الشهر فليصمه ومن كان مريضا أو على سفر فعدة من أيام أخر يريد الله بكم اليسر ولا يريد بكم العسر ولتكملوا العدة ولتكبروا الله على ما هداكم ولعلكم تشكرون
"O ye who believe, fasting obligatory upon you as required for those before you, that ye may be righteous. (That is) in a certain number of days. So if anyone among you sick or in transit (and then breaking it), then (wajiblah him fast) as many days left on the other days. And mandatory for people who are heavy run it (if they do not fast) ransom, (ie) to feed a poor man. Anyone who does good compliance, then that is better for him. And fast is better for you if ye only knew. (Some days it is specified) month of Ramadan, the month in which the derived (beginning) of al-Qur'an as a guidance for mankind and explanations of instructions and a differentiator (between the Truth and falsehood). Therefore, whoever of you is present (in a country where he lived) in the month, and whoever sick or traveling (and then he broke), then (wajiblah him fast), as much as the day he left behind, on the other days. Allah wants ease for you, and does not want hardship for you. And be ye glorify God for His guidance is given unto you, that ye may be grateful. "[Al-Baqarah: 183-185]
It has been narrated from Ibn 'Umar radi anhuma, he said that the Prophet sallallaahu' alaihi wa sallam said:
بني الإسلام على خمس, شهادة أن لا إله إلا الله وأن محمدا رسول الله, و إقام الصلاة, وإيتاء الزكاة, وحج البيت, و صوم رمضان.
"Islam is founded on five principles, which bear witness that no god has the right to be worshiped properly except Al-lah and Muhammad is the Messenger of Allah, establishing prayer, issued alms, pilgrimage to the House and fasting during Ramadan." 
And people have agreed on the obligation of fasting month of Ramadan, and he is one of the pillars of the pillars of Islam which has been known from the religion for sure. Anyone who denies his duty, then he has disbelieved or out of Islam. 
From Abu Hurayrah radi anhu, he said, the Prophet sallallaahu 'alaihi wa sallam said:
من صام رمضان إيمانا واحتسابا غفر له ماتقدم من ذنبه.
"Anyone who fasts Ramadan with faith and hope reward, undoubtedly his sins that have passed will be forgiven." 
It was narrated from Abu Hurayrah radi also anhu that the Prophet sallallaahu 'alaihi wa sallam has said: "Allah Almighty berfiman:
كل عمل ابن آدم له إلا الصيام فإنه لي وأنا أجزى به, والصيام جنة, فإذا كان يوم صوم أحدكم فلا يرفث ولا يصخب ولا يجهل, فإذا شاتمه أحد أو قاتله فليقل إني صائم, مرتين, والذي نفس محمد بيده لخلوف فم الصائم أطيب عند الله يوم القيامة من ريح المسك. وللصائم فرحتان يفرحهما: إذا أفطر فرح بفطره, وإذا لقي ربه فرح بصومه.
"Every charity children of Adam is for himself except fasting, where fasting is for Me and I will give you reward it. Fasting is a shield, if on day one of you fasting, then he should not utter obscenities , make noise and do not also do anything stupid people. And if there are people who mencacinya or attack, then let him say, 'Actually I was fasting.' -Twice-For the Lord is the soul of Muhammad in His hand, the real smell of the fasting person's mouth is more fragrant with Allah on the Day of Judgement than the scent of oil kasturi. For people who are fasting, there are two fun, if you break the fast, he rejoice with berbukanya and if he also met with his Lord happy with his fast. '"
Also from Sahl ibn Sa'd radi anhu, that the Prophet sallallaahu 'alaihi wa sallam said:
إن في الجنة بابا يقال له الريان يدخل منه الصائمون يوم القيامة لايدخل منه أحد غيرهم يقال: أين الصائمون? فيقومون لا يدخل منه أحد غيرهم, فإذا دخلوا أغلق فلم يدخل منه أحد.
"Verily in Paradise there is a door that is named ar-Rayyan. From the door of people who fast will enter on the day of Judgement later, no one who went through the door besides them. It is said to them, 'Which of the people who fasted?' Then they stood up (to enter), no one who went through the door in addition to them, when they had entered, the door was closed and nothing makes them apart. " 
3. Because Ramadan Fasting Mandatory Viewing Hilal (Moon)
It was narrated from Abu Hurayrah radi anhu, he said, the Prophet sallallaahu 'alaihi wa sallam said:
صوموا لرؤيته وأفطروا لرؤيته, فإن غمي عليكم الشهر فعدوا ثلاثين.
"Fast as you have seen it (the moon) and eat because you have seen it anyway. And if the moon was hidden from view you, then calculate the month (Sha'ban) to 30 days. "
4. Defined By What Month?
Ramadan is set by looking at the moon (the moon), although that view is only one person who trusted or the numbers to fulfill a 30-day month of Ramadhan. It has been narrated from Ibn 'Umar radi anhu, he said, "People are trying to see the new moon, and then I told the Prophet sallallaahu' alaihi wa sallam that I have seen it, then he fasted and ordered the men to fast." . If the moon can not be seen due to cloudy or the other, then the numbers fulfilled Ramadhan month to 30 days, based on the hadith of Abu Huraira that has past.
As for the month of Shawwal, it is not defined except by the testimony of two people. It was narrated from 'Abdur-Rahman ibn Zayd ibn al-Kahthtab, that he berkhutbah on the day in question to fast to him, and said, "Know that I have been with the Companions of the Prophet sallallaahu' alaihi wa sallam and I've asked them, then they told me that the Prophet sallallaahu 'alaihi wa sallam has said:
صوموا لرؤيته وأفطروا لرؤيته, وانسكوا لها, فإن غمى عليكم فأتموا ثلاثين يوما, فإن شهد شاهدان مسلمان فصوموا وأفطروا.
"Fast as you have seen it (the moon) and eat because you have seen it all, and beribadahlah because to see it. If the moon was hidden from view you, then genapkanlah to 30 days. And if there are two Muslims who testified (see the moon), fasting and eat you. '"
Narrated from the Governor of Mecca al-Harith bin Hatibz, he said, "The Messenger sallallaahu 'alaihi wa sallam has mandated it to us so that we serve based on sighting the moon. If we can not see it and have testified the two men who trusted (that they have seen it), then we worship according to the testimony of both of them. "
In his saying that reads "And if there are two people who gave testimony (see the moon), fasting and eat you" from the hadeeth of 'Abdur-Rahman bin Zayd. And his saying, "If we can not see it (the moon) and has testified the two men who trusted (that they have seen it), then we worship according to their testimony is." In the hadeeth of al-Harith, they gave the sense that there should be set a time of fasting and breaking (entering Shawwal) with the testimony of one person only, except for the fast determination of the time because there have been arguments that allow it (the testimony of one person), whereas no time to break the there are arguments menunukkan it, then he remains in legal origin (ie should the testimony of two people who trusted).
At this point of the book Tuhfatul penukilan Ahwadzi (III/373-374), with minor changes.
Anyone who saw the new moon alone, then let him fast until the other man who fasted. So did not he break the fast until they break, based on the history of Abu Hurayrah that the Prophet sallallaahu radi alaiahi anhu wa sallam has said:
الصوم يوم تصومون والفطر يوم تفطرون, والأضحى يوم تضحون.
"Time is a day of fasting in which you are all fast, time to break the ('Eid ul-Fitr) is the day you're all broke, and the day of' Eid al-Adha is a day where you sacrifice." 
[Copied from the book Al-Sunnah wal Wajiiz FII Fiqhis Kitaabil Aziiz, author Azhim Shaykh ibn Abdul al-Khalafi Badawai, edition of Indonesia Guide Complete Fiqh, Translation Team Tashfiyah LIPIA - Jakarta, Reader Publishers Ibn Kathir, Ramadan First published in 1428 - September 2007M]
. Takhrijnya has passed on the book of ath-Thaharah.
. Fiqhus Sunnah (I/366).
. Agreed upon: al-Bukhari Shahiih (Fat-Hul Baari) (IV/115, no. 1901), Sunan an-Nasa-i (IV/157), Sunan Majah Ibni (I/526, no. 1641), Shahiih Muslim (I/523, no. 760).
. Agreed upon: al-Bukhari Shahiih (Fat-Hul Baari) (IV/118, no. 1904), Muslim Shahiih (II/807, no. 1151 (164), Sunan an-Nasa-i (IV/163). Al-Junnah, with mendhammahkan jiim letter, it means prevention and obstructions. Ar-Rafatsu, to form a line ataskan letter ra ', fa' and tsa ', that is a dirty word. La yajhal, that he did not do anything stupid people like shouting, brash or anything else. Al-khuluf, ie mouth odor changes the fasting person because of his fast (Fat-Hul Baari, IV/125, 26, 127, cet. Darul ma'rifah).
. Agreed upon: al-Bukhari Shahiih (Fat-Hul Baari) (IV/111, no. 1896) and this is lafazhnya, Shahiih Muslims (II/808, no. 1152), Sunan at-Tirmidhi (II/132, no . 762), Sunan Majah Ibni (I/525, no. 1640), Sunan an-Nasa-i (IV/168) with lafazh the same and there is little extra.
. Agreed upon: Muslim Shahiih (II/762, no. 1081 (19) and this is his lafazh, Shahiih al-Bukhari (Fat-Hul Baari) (IV/119, no. 1909), Sunan an-Nasa-i (IV/133).
. Saheeh: [Irwaa-ul Ghaliil (no. 908)], Fiqhus Sunnah (I/367), and this in-riwayatkan hadith by Abu Dawud (VI/468, no. 2325).
. Saheeh: [Shahiih al-Jaami'ish Shaghiir (no. 3811)], Ahmad (al-Fat-hur Rabbaani IX/264 and 265/50), Sunan an-Nasa-i (IV/132 and 133) without a sentence: مسلمان.
. Saheeh: [Sunan Abi Dawud Shahiih (no. 205), Sunan Abu Dawud (VI/463, no. 2321).
. Saheeh: [Shahiih al-Jaami'ish Shaghiir (no. 3869)], Sunan at-Tirmidhi (II/101, no. 693) and he said, "According to some scholars, this Hadith is our intention to fast and break the fast with- together with the congregation and the people. "