Perform gusul properly and thoroughly without leaving any part unclean or untouched during ablutions .

This hadith emphasizes the importance of performing ghusl, a ritual bath, properly and thoroughly. It was narrated by 'Ali ibn Abi Talib that he heard Prophet Muhammad say that whoever leaves a space the size of a hair when doing ghusl for janabah and does not make water reach it, Allah will punish him with such and such in the Fire. From this hadith we learn that it is important to be thorough when performing any religious act or ritual as Allah will not accept anything less than perfection from us. We must take care to ensure that no part of our body is left unclean or untouched during our ablutions so as to avoid punishment in the hereafter.