Question: A theologian who is notorious for his opinions that are contrary to the rules of Islam wrote in his column that passing wind does not break wudu'. Is there not a hadith about it? What do the four madhhabs say about it?
ANSWER
Passing wind breaks wudu' according to all of the four madhhabs. (Al-Fiqh 'Ala al-Madhahib al-Arba'ah)

There are hadith-i sharif on this issue, some of which are as follows:

(If a person passes wind when performing salat, he should break off salat, make wudu', and repeat his salat.) [Tirmidhi, Nasai, Abu Dawud, Imam-i Ahmad, Bayhaqi, Tabarani]

(The wudu' of a person passing wind becomes nullified.) [Abu Dawud, Imam-i Ahmad]

(Shaitan gently touches the anus of a person performing salat. That person thinks that he passed wind. In this case, do not break off your salat unless you hear a sound or smell an odor.) [Imam-i Ahmad]

(The salat of a person who is not in a state of wudu' will not be acceptable. When wind escapes from the anus with or without sound, hadath occurs; that is, wudu' is nullified.) [Bukhari]

(If a person feels a movement in his anus, he should not leave the mosque unless he hears a sound or smells an odor [he should continue with salat].) [Bukhari, Muslim, Abu Dawud, Tirmidhi, Nasai]