Muslims commit sins and evils when they forget the Hereafter; and that which keeps them on the straight path is remembrance of death and resurrection, Allah Almighty says: (So as for he who transgressed. And preferred the life of the world, Then indeed, Hellfire will be [his] refuge. But as for he who feared the position of his Lord and prevented the soul from [unlawful] inclination, then indeed, Paradise will be [his] refuge.), An-Nazi`at, 41-37.

The Messenger of Allah, pbuh, was always keen to remind us of the Hereafter; because this keeps us from indulging in sins, or delaying of repentance; through many steps, of which visiting graves; narrated Abu Dawood, ranked sahih by Al-Albani, on the authority of Buraydah who said that the Messenger of Allah, peace be upon him, said: "It happened that I forbade you to visit graves, but you are permitted now to visit it as it bears reminder"

narrated At-Tirmidhi, ranked sahih by Al-Albani, on  the authority of Buraydah who said that the Messenger of Allah, peace be upon him, said: "I happened that I forbade you to visit graves, I am permitted to visit the grave of my mother , so visit graves as they remind us of the hereafter"

This is a very important sunnah for both the alive and the dead; as for the alive, he remembers death and the hereafter; and the dead is benefitted from the supplication of the alive for him. Thus, the Prophet, pbuh, has been used to visit the graves of Al-Baqi` frequently so that he remembers the hereafter and invoke Allah for the dead which bears great benefit for both.