Is it obligatory to perform ablution upon feeling a movement in the stomach or hearing the sound of gas being released from the anus after or during ablution?

If a person is certain that gas has been released, then ablution (wudu') becomes obligatory. However, mere movement of gas in the stomach or an imagined release of it should be disregarded, based on the Prophet's (peace and blessings be upon him) saying: "Not unless he hears a sound or perceives a smell." This hadith (definition) is a fundamental principle that things remain in their original state until certainty of the contrary is established. A sudden doubt does not harm this. Giving attention to such doubts can lead to obsessive whispers (waswas). What is meant by "unless he hears a sound or perceives a smell" is that he must know with certainty that one of them exists, not merely hearing or smelling.