Ata’  rahimahullah said: “…And he should not chew gum, for if he swallows his saliva, I do not say that it will break his fast, but it is prohibited…”

[Saheeh Bukhar in mu’allaq form (without chain)]

Hafidh ibn Hajr rahimahullah said commenting on this statement:

“Ibn Mundhir said: They (the scholars) agreed that there is nothing on a fasting person in what he swallows from what runs with his saliva of what is between his teeth, that he is not capable of removing. Abu Hanifa said: If there is between his teeth meat, then he eats it deliberately, then there is no Qada (make-up) for him. The majority of Scholars differed with him because it is considered from food. The majority of Scholars permitted chewing gum if nothing of it seeps (down his throat). So, if something from it seeps, then he swallows it. The majority of scholars are upon the opinion that he breaks his fast…everything that is chewed and remains in the mouth like mastic and frankincense. So, if anything from it seeps down from the mouth, then enters inside, then he has broken fast. Otherwise it is a dehydrant and dipsetic (causing thirst) so it is disliked due to these considerations”

[Fath ul-Baari v.4, p. 198]

I say (Faisal): Imam Mundhir said in his book Ishraaf ‘ala mathaahib il-Ulamaa

Chapter: The Chewing of Gum by the Fasting person

“It was reported to us from Umm ul-Mumineen Aisha radiallahu anha and ‘Ata that they permitted the chewing of gum by the fasting person. It was reported to us from Ibn ‘Abbas radiallahu anhumaa that he said: there is no harm for a fasting women to chew for her child food. Hasan al-basri said the same, an-Nakha’ee, and Al-Awzaai said the same then he returned from it and disliked it.
The People of Opinion said: He fasts, the one who tastes something with his tongue. And (it being) disliked (to) chew gum for the fasting person are (the views of) ‘Ata, Sha’bi, an-Nakh’aee, Muhammad ibn Ali, Qatadah and Ahmad.
And Malik disliked that for the fasting person to touch with his tongue something that has taste, Shaafi’ee, Ishaaq and the people of Opinion disliked the fasting person chewing gum. So if he chews it, it does not break the fast”

[Volume 3, pg. 132-133 no. 1169]

I should also add that some of the chains of narrations for the statements of the salaf are weak, nonetheless Imam Mundhir shows that there is a scholarly difference on this issue. But as quoted earlier, Hafdih ibn Hajr said that majority are of the opinion that it is allowed to chew gum while fasting provided it does not seep down the mouth.

Finally a fatwa from ‘Allamah Yahya ibn ali al-Hajoori:
Question:

Does chewing bubble gum which doesn’t dissolve break a person’s fast?

Answer:

Our brother has worded the question in a way which means chewing gum isn’t food. No doubt swallowing candy breaks the fast. Conversely chewing sugar-less gum which doesn’t dissolve doesn’t break the fast. However this goes against the outward appearance of a fasting person. And perhaps the person’s saliva will dissolve the gum and make him tired from chewing it. The strongest evidence that chewing gum doesn’t break the fast is the statement from Ibn Abbaas (may Allah be pleased with him) who said, ‘The person fasting can taste food.” Tasting food is like chewing gum, but I don’t advise the fasting person to chew gum based on the previous reason why.

[Source]

Allah knows best.

Translated by

Faisal ibn Abdul Qaadir ibn Hasan
Abu Sulaymaan