Shaykh ‘Abdul-‘Aziz ibn Bāz, the Former Mufti of Saudi Arabia (rahimahullah) said:

There are many tremendous benefits and wisdoms in fasting, some of them are:

1) Fasting purifies the soul from bad manners and negative traits such as arrogance, pride, and stinginess, and makes it accustomed to noble manners such as patience, forbearance, generosity, and benevolence. Striving in what pleases Allāh and brings one closer to Him.

2) Fasting reveals to the individual their true self, their weaknesses, and their profound reliance on their Lord. It also reminds them of the great favours of Allāh upon them.

3) Fasting serves as a reminder of the needs of the less fortunate, causing gratitude towards Allāh. This gratitude prompts individuals to utilize Allāh’s blessings in obedience, aiding the needy, and practicing kindness towards them.

4) Fasting is a means to attain taqwa. The definition of taqwa is: Obeying Allah and His Messenger by doing what has been commanded with and avoiding what has been forbidden, doing so with sincerity (ikhlas) for Allāh, out of love of Allāh as well as hope and fear.

5) Fasting makes the passageways of the Shaytan in the body narrow [just as the passageways of the blood in the body are narrow due to fasting].

6) Fasting purifies the body by removing toxins and gives one good health and strength. This has been admitted by many doctors and they have used fasting to cure numerous illnesses.

Source: Majmū of Ibn Baz, by way of al-Ikhtiyārāt al-Fiqhiyyah compiled by Khalid ibn Su‘ūd al-‘Ajmī (pp. 310-311)