´It was narrated from Abu Hurairah that a man said to the Prophet:` "My father died and left behind wealth, but he did not leave a will. Will it expiate for him if I give charity on his behalf?"
Explanation & Benefits
Hafiz Muhammad Ameen
“This mistake” refers to not giving charity (sadaqah) and not making a bequest (wasiyyah) despite having abundant wealth. It has been counted as a sin in the sense that it is a deprivation from such a great reward which was entirely attainable. Or, it may mean general mistakes, i.e., will their sins be forgiven if I give charity?
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 3682