Sheikh Abdullah bin Abd al-Azhim Khalafi
The scholars have agreed that fasting is obligatory upon a Muslim who understands, baligh, healthy, and live (not travelers), and for a woman to let him pure from menstruation and childbirth. 
As for fasting is not obligatory for those who are not rational and not baligh, then based on the words of the Prophet sallallaahu 'alaihi wa sallam:
رفع القلم عن ثلاثة: عن المجنون حتى يفيق, وعن النائم حتى يستيقظ, وعن الصبي حتى يحتلم.
"It has lifted the pen of three groups: from a madman until he realized, from the bed until she woke up, and the little boy until he baligh." 
As for fasting is not obligatory upon those who are sick and wayfarers, then based on the word of Allah, the Exalted:
ومن كان مريضا أو على سفر فعدة من أيام أخر
"... And whoever sick or traveling (and then breaking it), then (wajiblah him fast), as much as the day he left behind, on the other days ... "[Al-baqa-rah: 185]
If people are sick and travelers are still fasting, then it has been inadequate, because they break their permissibility is a form of relief (rukhsa), and if they continue to implement a mandatory, then it is good.
6. Which Home For Those Over, Breaking Or Fast?
If people are sick and travelers do not have difficulty in fasting, fasting more mainstream, whereas if they find difficulty in fasting, then break their more mainstream.
It has been narrated from Abu Sa'eed al-Khudri radi anhu, he said: "We went to war with the Prophet sallallaahu 'alaihi wa sallam during Ramadan, among us there is a fast and there is a break. Those who fasted did not denounce the break, and vice versa are not denounce the fast break. They looked at each other, for people who have the power, fast is better for him. And for those who feel weak, then break the fast is better. "
As for fasting is not obligatory upon women's menstruation and childbirth, then based on the hadeeth of Abu Sa'eed radi anhu, that the Prophet sallallaahu 'alaihi wa sallam said:
أليس إذا حاضت لم تصل ولم تصم? فذلك نقصان دينها.
"Do not they (the women) menstruation if they're not praying and not fasting? That's what they lack in terms of religion. "
If women are menstruation and childbirth remain abstinent, then his fast is not enough they (not valid in this case), because fasting is one of the conditions of menstruation and childbirth sacred, and mandatory for them to mengqadha 'fast.
It was narrated from 'Aisha radi anhuma, he said, "Once in while we were having menstruation at the time of the Prophet sallallaahu' alaihi wa sallam, we were ordered to mengqadha 'fasting and we are not commanded to mengqadha' prayer." 
7. What Payers Do The Men's Old Homes And The Poor Old Woman, Also the Sick Absence Hope Cured
Those who are unable to fast due to advanced age or who semisalnya, then allowed him a break and feed the poor every day of the days he left behind, according to the word of God:
وعلى الذين يطيقونه فدية طعام مسكين
"... And a must for serious people who run it (if they do not fast) ransom, (that) feeding a poor ...." [Al-Baqarah: 184]
It was narrated from 'Atha', that he heard Ibn 'Abbas read a verse, then Ibn' Abbas said, "This verse does not mansukh (deleted jurisdiction), which meant the men and women who are elderly, where they are unable to fast, then they feed the poor every day of the days that ditinggalannya. "
8. Pregnant And Breastfeeding Women
Women who are pregnant and lactating women, if they are unable to fast or worried about their children when they are fasting, then it can for them both to break the fast and obligatory upon them to ransom, but they are not obliged mengqadha '. It was narrated from Ibn 'Abbas Radhiyalahu anhuma, that he said, "Given a relief to people who are old and frail old lady in it, are both able to fast not to fast if they want to and feed the poor every day and with no obligation qadha 'for both. Then the law is abrogated by the verse:
فمن شهد منكم الشهر فليصمه
"Whoever among you who is present in that month (Rama-dhan), then let him fast." [Al-Baqarah: 185]
And has been established for people who are elderly and frail elderly women, if they are not capable of fasting. Also for women who are pregnant and lactating women, if they worry, then they should not fast and should feed a poor person every day. "
Also narrated from Ibn 'Abbas radi anhuma, he said, "If a pregnant woman worried about himself, so also concerned about women who breastfeed their children during the month of Ramadan, then it should be for both of them to break, and then feed the poor every day of the days that he left behind and no obligation on them mengqadha 'fasting. "
From Nafi 'radi anhu, he said, "One of the daughter of Ibn' Umar radi anhu became the wife of a man of Quraysh, and in Ramadan when she was pregnant, then she was thirsty, so Ibn 'Umar ordered him to break the fast and feed a poor person every day (left). "
9. Food size Mandatory Issued
It was narrated from Anas Ibn Malik radi anhu, that he had been unable to eat for a year (30 days in the month of Ramadan-pent.), So he will make a big bowl of porridge and call 30 people were poor to make them all full. 
[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]
. Fiqhus Sunnah (I/506) cet. ar-Rayyan
. Saheeh: [Shahiih al-Jaami'ish Shaghiir 3514], Sunan at-Tirmidhi (II/102/693).
. Saheeh: [Shahiih Sunan at-Tirmidhi (no. 574)], Shahiih Muslims (II/787, no. 1116 (96)), Sunan at-Tirmidhi (II/108, no. 708).
. Saheeh: [Mukhtasar Shahiih al-Bukhari (no. 951], Shahiih al-Bukhari (Fat-Hul Baari) (IV/191, no. 1951).
. Saheeh: [Shahiih Sunan at-Tirmidhi (no. 630)], Shahiih Muslims (I/265, no. 335), Sunan Abi Dawood (I/444, no. 209, 260), Sunan at-Tirmidhi (II/141 , no. 784), Sunan an-Nasa-i (IV/191).
. Saheeh: [Irwaa-ul Ghaliil (no. 912)], Shahiih al-Bukhari (Fat-Hul Baari (VIII/179, no. 4505).
. Sanadnya strong: HR. Al-Bayhaqi (IV/230).
. Saheeh: Shaykh al-Albani in Irwaa propped-ul Ghaliil (IV/19) to Tabari (no. 2758) and he said sanadnya sahih according to Muslim requirements.
. Sanadnya saheeh: [Irwaa-ul Ghaliil IV/20], ad-Daraquthni (II/207, no. 15).
. Sanadnya saheeh: [Irwaa-ul Ghaliil IV/21], ad-Daraquthni (II/207, no. 16).