Overall meaning
As al-Nawawī (d. 676 AH) pointed out, this ḥadith is one of the great universal maxims of Islam and a foundational principle upon which many far-reaching rulings are built. The rule is that whatever has been established with certainty remains as it is; one does not abandon that certainty on the basis of mere doubts or misgivings, whether those doubts are strong or weak, so long as they do not rise to the level of certainty. The applications of this rule are many and well known, and this ḥadith is one of them.

Thus, if a person is certain that he is in a state of ritual purity and then doubts whether he has broken it, the default verdict is that his purity remains. Conversely, if he is sure he has broken it and later doubts whether he performed ablution, the default is that the nullification stands. The same applies to garments and places: their original status is purity unless definite impurity is proved. The rule also governs the number of rakʿahs in prayer: if one is certain of having prayed three and doubts the fourth, the presumption is that the fourth has not been performed. It likewise applies to divorce: if a man doubts whether he divorced his wife, the marriage bond remains intact. Many other cases follow the same pattern.

Lessons drawn from the ḥadith

1. The general maxim: “The original state remains as it was.”
2. Mere doubt about a nullifying act does not break wuduʾ or invalidate the prayer.
3. It is forbidden to leave the prayer without a clear, recognized reason.
4. Wind emitted from the anus, whether audible or silent, nullifies wuduʾ.
5. The words “hearing a sound or detecting an odor” in the ḥadith refer to achieving certainty. If one attains certainty by some other means, even without hearing or smelling anything, his wuduʾ is nullified.

The ruling on the urine of a male and female infant
Umm Qays bint Miḥṣan al-Asadiyyah reported that she brought her infant son, who had not yet eaten solid food, to the Messenger of Allah ﷺ. The Prophet ﷺ seated the child in his lap, whereupon the boy urinated on his garment. He then called for some water and sprinkled it over his garment without washing it.

In another report from ʿĀʾishah, Mother of the Believers, it is related that the Messenger of Allah ﷺ was brought a baby boy who urinated on his garment