Here a few useful notes the first few chapters of ‘Kitab as-Sawm’ in ‘Fath al-Bari’ (4/123 onwards):
1 – The lexical and Shar’i definitions of الصوم:
“Linguistically, siyam is to refrain from something. Shar’an, it is to hold back from something specific for a specific amount of time, under specific conditions…it is said to the knight who has refrained from joining an expedition for some time that he is sa’im. And in the Shar’, it is that one who is tasked with this obligation is to refrain from food, drink, sexual pleasure, and vomiting from sunrise to sunset.”
2 – Fasting is a shield:
“…and the narrations that are related to this show that it is a shield from the Hellfire, and this is what Ibn ‘Abd al-Barr opined.
As for the author of ‘an-Nihayah,’ he said: “What is meant by it being a shield is that it protects the person from the desires that can harm him.”
al-Qurtubi said: “It is a curtain.” So, it is a must for the one fasting to avoid that which will corrupt him and decrease his reward…
ِِAnd al-’Iyad said in ‘al-Ikmal’: “It is a shield from sins or the Fire, or both of these,” and an-Nawawi took this opinion.”
3 – The meaning of “…و لا يجهل…”:
“This means that he should not do anything that is customary of the ignorant people, such as making foolish noises, fooling around, etc…al-Qurtubi said: “It is not to be understood here that this is allowed when one is not fasting. Rather, it is even more incumbent to avoid such things when one is fasting.”"
4 – The various levels of fasting:
“And Ibn al-’Arabi narrated from some of the ascetics that they said that fasting is of four types:
1) the fast of the layman, and that is from food, drink, and sex;
2) the fast of the chosen among the layman, and that is by avoiding all the forbidden statements and actions;
3) the fast of the chosen people, and that is to abstain from everything but the remembrance and worship of Allah; and
4) the special fast of the chosen people, and that is to fast from anything other than Allah, and there is no breaking of this fast until the Day of Resurrection.”"
5 – The meaning of “Whoever fasts Ramadan out faith, and awaiting his reward…”:
“What is meant by ‘out of faith’ is that he deeply believes in fasting being an obligation, and ‘awaiting his reward’ is that he seeks the reward from Allah.
al-Khattabi said: “This means he should be energetic and willful, and should fast with the hope of getting a reward and purifying his soul, and he should not look at fasting as a burden, and should not be counting the days until Ramadan is over.”"
6 – “The fasting person has two instances of joy: when he breaks his fast, and when he meets his Lord”:
“al-Qurtubi said, in regards to the joy of breaking the fast, that this is because his hunger and thirst are gone since he can now break his fast, and this is a natural type of happiness. It is also said that his happiness at breaking his fast is because he has completed his worship, been relieved from his Lord, and knows that he is able to fast again with help from Him.
I say that it is possible that the issue is more general than what has been mentioned, as each person’s happiness is in accordance with his different level in regards to his worship. So, there are some that express the permissible happiness, which is the natural joy of being able to eat, and some people express the happiness that is preferred…”