It does not break the fast; because this is something that cannot be avoided. However, it is advisable for him to spit once after expelling the water before swallowing his saliva; because the water mixes with the saliva and does not come out just by expelling it. It is not required to exaggerate in spitting; because what remains after that is merely moisture and dampness that cannot be avoided, as mentioned in Bada'i al-Sana'i 2: 90, and Radd al-Muhtar 2: 98.