Musnad Ishaq

Benefits:
The aforementioned hadith clearly demonstrates the virtue of fasting, and it is understood that good deeds lead to the forgiveness of sins. In the mentioned hadith, ((As-Sawmu Li)), it is because fasting is such an act in which there is no room for ostentation or showing off; a person abandons all his desires purely out of fear of Allah Ta’ala. The scholars have said: “Fasting is for Me” is stated to indicate the abundance of reward for fasting.

Imam Sufyan al-Thawri rahimahullah was asked about the meaning of “As-Sawmu Li” (Fasting is for Me). He replied: Fasting is essentially patience (sabr); a person refrains from eating, drinking, and fulfilling his needs in a lawful manner, and the reward for patience is given without measure. Then he rahimahullah recited this verse of the Noble Qur’an: “Indeed, the patient will be given their reward without account.” (: Az-Zumar: 10).... “Those who are patient will be given their reward without measure.” (Sharh as-Sunnah: 6/335)

There can be several reasons for “As-Sawmu Li” (Fasting is for Me), meaning that in other acts of worship, obedience is predominant, while in fasting, love is predominant. The signs of love are gathered in the fasting person, and there are six signs of lovers:
(1) Sighing deeply. (2) The complexion becoming pale. (3) The eyes becoming moist. (4) Eating less. (5) Speaking less. (6) Sleeping less.

These aforementioned signs are also found in a fasting person. The reward for an obedient servant is recompense, but the reward for a lover is the meeting with the beloved. In other acts of worship, ostentation is possible, but in fasting, there is no ostentation. On the Day of Resurrection, other acts of worship can be taken by those who have rights over a person, as mentioned in the ahadith, but the fast will not be given to anyone with a right; Allah, the Possessor of Majesty, will say that the fast is Mine, it will not be given to anyone. Disbelievers and polytheists would perform other acts of worship for idols, such as sacrifice, prostration, pilgrimage, and charity, but no disbeliever would fast for an idol.

(Mirqat Sharh Mishkat, Ashi‘at al-Lam‘at Sharh Mishkat, summarized)

In “Ana Ajzi Bihi” (I Myself am its reward or I will give its reward), it means that on the Day of Resurrection, the fasting people will be granted My vision and pleasure. And Allah knows best.

It is understood that the odor from the mouth of the fasting person is more fragrant to Allah than musk.

Khaluf: The odor that comes from the mouth due to not eating or drinking for a long time is called khaluf. Some people hold the view that one should not use the miswak (tooth-stick) while fasting because it removes this odor. However, this is not correct, because this odor is due to the emptiness of the stomach and is not related to the use of the miswak.