Silsilah as-Sahihah 723 — Praying without Wudu is a grave sin

It is narrated from Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: “It was ordered concerning one of the servants of Allah that he be given a hundred lashes in his grave. He kept asking (for reduction) and kept praying, until only one lash remained (the rest were forgiven). When this one lash was given to him, his grave was filled with fire. When the effect (of the punishment) subsided and he regained consciousness, he asked, ‘(O angels!) For what reason did you lash me?’ They said, ‘You had once performed a prayer without ablution, and you passed by an oppressed person but did not help him.’”