Ibn Majah

Benefits and Issues:

➊ Paradise has eight gates.
These are attributed to various good deeds.
For example: Bab al-Salat (the gate of prayer),
Bab al-Jihad (the gate of jihad),
Bab al-Sadaqah (the gate of charity).
See: (Sahih al-Bukhari, al-Sawm, Chapter: Al-Rayyan for those who fast, Hadith: 1897)

➋ A person who gives special importance to a particular good deed
and strives more in its performance,
will enter Paradise through the gate associated with that deed.
If he possesses multiple such qualities,
he will be called from more than one gate.
For example, Abu Bakr radi Allahu anhu will be called from all eight gates. (Sahih al-Bukhari, al-Sawm, Chapter: Al-Rayyan for those who fast, Hadith: 18973)

Rayyan means “quenched” or “well-watered.”
The fasting person endures hunger and thirst,
and enduring thirst is more difficult than enduring hunger,
therefore, the gate designated for those who fast has been named the gate of quenching (al-Rayyan).

➌ Along with fulfilling obligatory acts of worship,
one should also perform the recommended (sunnah) voluntary acts of worship as much as possible.
Observance of voluntary acts of worship is a means of entering Paradise.

Hadith Commentary:
➊
The name "Rayyan" has been given to this gate because those who fasted endured thirst in the world. When they pass through Bab al-Rayyan and enter Paradise, and drink from the river of Paradise, they will attain such satiation that they will never feel thirst again. In any case, the eight gates of Paradise have been mentioned in numerous ahadith. All these gates are divided according to people's deeds: whoever performed abundant prayers will pass through Bab al-Salat, and whoever engaged frequently in jihad will be invited to enter Paradise through Bab al-Jihad.
(: ‘Umdat al-Qari: 10/612)

➋
The description of the gates of Paradise in the ahadith is such that the two panels of each gate will be at a distance of forty years’ journey from each other.
(: Fath al-Bari: 6/396)

Hadith Commentary:

The word "Rayyan" is derived from "ray," which means satiation (of thirst). Since the hardship of thirst in fasting is a particular hardship, its true compensation can only be "Rayyan," through which satiation is attained. Therefore, this gate will be exclusively for those who fast; by entering through it, they will become satiated—completely satiated—and thereafter, they will never feel thirst for all eternity.

May Allah make us among them. Ameen.

Hadith Commentary:
(1)
Rayyan means "satiation" or "quenching of thirst."
Since those who fast endure hunger and thirst in this world for the sake of Allah, they will be made to pass through this gate of satiation with great honor and respect, and as they pass through, they will be given such a drink that they will never feel thirst again. Thus, it is mentioned in the hadith that whoever enters through this gate will be given a drink, and whoever drinks it will never feel thirst again.

(2)
In a narration of Sahih Muslim:
Whoever performs ablution (wudu) properly and recites the supplication, all eight gates of Paradise are opened for him, and he may enter Paradise through whichever gate he wishes.
(Sahih Muslim, Al-Taharah, Hadith: 553(234))

From this hadith, it appears that "Bab al-Rayyan" is not exclusive to those who fast.
The answer to this is that a person who performs ablution will not even intend to pass through Bab al-Rayyan.
('Umdat al-Qari: 16/8)

Hadith Commentary:
Benefits and Issues:
The greatest discomfort felt during fasting is thirst; therefore, the reward and recompense for fasting will be given in such a way that the most prominent and dominant aspect will be satiation. In accordance with this, the gate of Paradise that has been designated specifically for those who fast is named "Rayyan" (completely and abundantly satiated).

1:
By "those who fast" are meant those people who, along with the obligatory fasts, also frequently observe voluntary (nafl) fasts in abundance.
Otherwise, the obligatory fasts of Ramadan are necessary for every Muslim.
This special virtue is reserved only for those who, in addition to the obligatory fasts, are diligent in frequently observing voluntary fasts.

(1) In this narration, those referred to as fasting people are those who habitually observe voluntary (nafl) fasts, because all Muslims observe the obligatory (fard) fasts.

(2) The specific gate is designated for those who fast in order to grant them distinction, just as a special entrance is reserved for honored guests.

(3) “Rayyan” means: the gate of satiation. It is as if, upon entering through this gate, satiation will be attained—whether by the act of entering itself or by drinking. Whereas those who enter through the other gates will receive water inside Paradise.

(4) “He will never be thirsty again.” Thereafter, drinking water will be for pleasure, not to quench thirst. This virtue is granted to them because they remained thirsty for the sake of Allah’s pleasure. In fasting, thirst is felt most intensely.