Mishkat al-Masabih #1927

‘Ata’ said, “If one rinses his mouth and ejects the water in it, swallowing his saliva and anything that remains in it does him no harm; but one should not chew gum, for although I do not say that he breaks his fast he swallows the saliva produced by the gum, he is nevertheless prohibited from doing it.” Bukhari transmitted it in a chapter heading.