Сахих аль-Бухари #96

Once Allah's Messenger (ﷺ) remained behind us in a journey. He joined us while we were performing ablution for the `Asr prayer which was over-due. We were just passing wet hands over our feet (not washing them properly) so the Prophet (ﷺ) addressed us in a loud voice and said twice or thrice, "Save your heels from the fire