وَيْلٌ لِلْأَعْقَابِ مِنَ النَّارِ
Meaning: A severe warning concerning heels left inadequately washed.
The source cites the report in the context of people failing to wash their feet properly. It is used to support the duty to wash bare feet rather than merely wipe them.
The commentary also refers to a report from Ali concerning the washing of the feet.