Reference: Fataawa Ramadhaan – Volume 2, Page 535, Fatwa No.508;
Fataawa as-Siyaam libni-Jibreen – Page 45
Question: One day, [when making ablution] I swallowed some water after gargling and when I asked a Shaykh [about it], he told me there was no harm in this since I did not intend to break my fast. So is there anything required of me?
Response: You do not have to make up this fast because of that, and what the Shaykh advised you, is correct. Firstly, because you did not know about the ruling. Secondly, because of the small amount [of water]. And thirdly, because it transpires that this is similar to being overcome (out of one’s control).