Imam Ahmad—may Allah have mercy on him—said, “On this issue there are two authentic hadiths from the Messenger of Allah ﷺ.”

As for eating the meat of animals other than camels, it does not invalidate wudu.

There are, however, several matters about which the scholars have differed as to whether they nullify wudu: touching one’s private part, touching a woman with desire, washing the deceased, and apostasy from Islam. Some scholars hold that each of these acts breaks wudu, while others maintain that it does not. The question is open to investigation and ijtihad, yet making wudu after any of them, in order to avoid the point of disagreement, would be better.

One important issue related to this subject remains: if someone is certain of his state of purity but then doubts whether a nullifier has occurred, what should he do?

It is firmly established from the Messenger of Allah ﷺ—in the hadith narrated by Muslim from Abu Hurayrah (may Allah be pleased with him)—that he ﷺ said: “If any one of you feels something in his abdomen and is unsure whether anything has come out, he should not leave the mosque until he hears a sound or perceives an odor.”

This noble hadith and others like it indicate that when a Muslim is sure he is in a state of purity yet doubts that it has been broken, he remains on his original purity. Purity is the baseline and is certain, whereas the occurrence of a nullifier is doubtful; and certainty is not removed by doubt.