The Prophet (ﷺ) used to check his companions' worship just like a teacher who used to check his students' progress. It was his habit to teach them his teachings and rectify their mistakes. In this hadith, Omar ibn Al-Khattab narrated that when a man performed ablution but missed washing a spot equal to a toenail (a metaphor for a small size), the Prophet (ﷺ) referred to this mistake and said, "Go back and perform ablution properly." The man completed his ablution (or repeated it as said) and prayed after the Prophet (ﷺ) accepted his ablution. Finally, this hadith contains the following benefits: (1) It illustrated how the Companions rapidly responded to implement the Prophet's commands, (2) It urges us to complete ablution and warns against neglecting to wash even a small spot of ablution parts, and (3) It clarifies how imams and scholars should teach common people the matters of Islam and rectify their mistakes..