Imam An Nawawi says in Sharh Muslim:

“If it may be said the ablution expiates (the sins), then what does the prayer expiate? If the prayer expiates the sins, then what does the congregations and Ramadan expiate? Similarly, fasting the day of Arafat is an expiation for two years and the day of Ashuraa is an expiation of one year. Also, if one’s Tameen (saying Ameen in prayer) is in accordance to that of the angels, will his previous sins be forgiven?

The answer:

That which some of the scholars have answered with is that all of these aforementioned acts are from that which expiates. Thus, if it is found that which expiates the minor sins, even if he hasn’t committed a minor sin nor a major one, then good deeds are written for him, and his levels are raised.

If he has fallen into a major sin or major sins whilst not falling into a minor sin, then we hope that it lightens the major sins. And Allah knows best.

[Sifat Wudu an Nabi of Shaykh Abdullah al Iryaani pg. 18]

Translated by

Majid Jawed Al-Afghanee
Abu Layl