Praise be to Allah.
Man’s life is divided into three sections:
1 – The life of this world, which ends with death.
2 – The life in al-barzakh, which starts after death and ends when the Hour begins.
3 – The life of the Hereafter, which begins after the people are raised from their graves, and is spent either in Paradise (we ask Allaah of His Bounty) or in Hell (we seek refuge with Allaah).
So the life of al-barzakh lasts from after a person dies until he is resurrected, whether he is buried in a grave or not, whether he is burned or eaten by wild animals. The evidence that points to this life is the hadeeth narrated from the Prophet (peace and blessings of Allaah be upon him), who said that after the deceased is placed in his grave, he can hear the footsteps of his family (as they walk away from the grave).
This life (in al-barzakh) will either be filled with delight, or it will be hellish, and the grave will either be one of the gardens of Paradise or one of the ditches of Hell.
What indicates that there will be either delight or torment (in al-barzakh) is the aayah in which Allaah says concerning the people of Pharaoh:
“The Fire, they are exposed to it, morning and afternoon. And on the Day when the Hour will be established (it will be said to the angels): ‘Cause Fir‘awn’s (Pharaoh) people to enter the severest torment!’”
[Ghaafir 40:46 – interpretation of the meaning]
Ibn Mas’ood said: The souls of the people of Pharaoh and those of their ilk among the kaafirs are shown the Fire morning and evening, and they are told, this is your abode.
Ibn Katheer said: this aayah is the main basis of the Sunni’s belief in the torment of al-barzakh in the grave.
(Tafseer Ibn Katheer, 4/82)
Al-Qurtubi said: Some of the scholars quoted as evidence to prove the torment of the grave the phrase “The Fire, they are exposed to it, morning and afternoon” [Ghaafir 40:46]. A similar view was expressed by Mujaahid, ‘Ikrimah, Muqaatil and Muhammad ibn Ka’b, all of whom said that this aayah is proof of the torment of the grave. Do you not see that it says concerning the torment of the Hereafter: “And on the Day when the Hour will be established (it will be said to the angels): ‘Cause Fir‘awn’s (Pharaoh) people to enter the severest torment!”? (Tafseer al-Qurtubi, 15/319)
It was narrated that ‘Abd-Allaah ibn ‘Umar (may Allaah be pleased with him) said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said: ‘When any one of you dies, he is shown his place morning and evening. If he is one of the people of Paradise then he is one of the people of Paradise, and if he is one of the people of Hell, then he is one of the people of Hell.’” (Narrated by al-Bukhaari, Bid’ al-Khalq, 3001; Muslim, al-Jannah wa sifat na’eemihaa, 2866).
It was narrated from ‘Aa’ishah (may Allaah be pleased with her) that a Jewish woman entered upon her and mentioned the torment of the grave, and said to her, “May Allaah protect you from the torment of the grave!” ‘Aa’ishah asked the Messenger of Allaah (peace and blessings of Allaah be upon him) about the torment of the grave, and he said, “Yes, the torment of the grave.” ‘Aa’ishah (may Allaah be pleased with her) said: “I never saw the Messenger of Allaah (peace and blessings of Allaah be upon him) pray any prayer after that but he sought refuge with Allaah from the torment of the grave.” (Narrated by al-Bukhaari, al-Janaa’iz, 1283; Muslim, al-Kusoof, 903).
These aayahs and ahaadeeth indicate that the torment of the grave is real and that it is ongoing in the case of some people.
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him and save him from the torment of the grave) said:
If a person is a kaafir (we seek refuge with Allaah), then there is no way that the delight will ever reach him, and his torment will be continuous. If a person was a sinner but he was a believer, then his torment in the grave will be commensurate with his sin, and perhaps the punishment for his sin will take less time than the time in al-barzakh between his death and the onset of the Hour, in which case it will cease.
(al-Sharh al-Mumti’, vol. 3, p. 253)
See also the answer to Question no. 7862, where more details are given.