When the son of Adam dies and his soul departs and he is placed in his grave, then he is in the first stage of the Hereafter, because the grave is the first of the stages of the Hereafter.

It was narrated that Hani’, the freed slave of ‘Uthman Ibn ‘Affan said: "When ‘Uthman Ibn ‘Affan stood by a grave he would weep until his beard became wet. It was said to him, “You remember Paradise and Hell and you do not weep, but you weep because of this?” He said: “The Messenger of Allah said: ‘The grave is the first of the stages of the Hereafter; whoever is saved from it, what comes afterwards will be easier for him, but if he is not saved from it, what comes afterwards will be worse for him.’” And the Messenger of Allah said: “I have never seen any scene but the grave is more frightening than it.” [At-Tirmithi]

In the grave, two angels, who are charged with questioning, come to him and ask him what he used to believe in this world, who was his Lord, what was his religion and who was his Prophet. If he gives a correct answer, that saves him, but if he does not answer them they inflict a severe and painful beating on him.

If he was one of the righteous, angels with white faces come to him, but if he was one of the evildoers, angels with dark faces come to him. This is one of the tribulations that he will suffer through.

It was narrated from ‘Aa’ishah that the Prophet used to say: “O Allah! I seek refuge with You from laziness and old age, and from debts and sins; from the torment of the Fire and from the tribulation of the Fire, and from the tribulation of the grave and the torment of the grave, and from the evil of the tribulation of wealth, and from the evil of the tribulation of poverty, and from the evil of the tribulation of the Dajjal (Antichrist). O Allah! Wash away my sins with the water of snow and hail, and cleanse my heart from sin as a white garment is cleansed from filth, and put a great distance between me and my sins, as great as the distance You have made between the East and the West).” [Al-Bukhari]

Ibn Hajar said: “The phrase 'from the tribulation of the grave' means the questioning of the two angels.”

With regard to the questions that the angels will ask in the grave, this is explained clearly in the following narration. It was narrated that the companions Al-Baraa’ Ibn 'Aazib said: "We went out with the Messenger of Allah for the funeral of a man from among the Ansar (inhabitants of Madeenah). We came to the grave and when (the deceased) was placed in the grave the Messenger of Allah sat down and we sat around him, as if there were birds on our heads (i.e., quiet and still). In his hand he had a stick with which he was scratching the ground. Then he raised his head and said: “Seek refuge with Allah from the torment of the grave”, two or three times. Then he  said, “When the believing slave is about to depart this world and enter the Hereafter, there come down to him from heaven angels with white faces like the sun, and they sit around him as far as the eye can see. They bring with them shrouds and perfumes from Paradise. Then the Angel of Death comes and sits by his head, and he says, ‘O good soul, come forth to forgiveness from Allah and His pleasure.’ Then it comes out easily like a drop of water from the mouth of a water-skin. When he seizes it, they do not leave it in his hand for an instant before they take it and put it in that shroud with that perfume, and there comes from it a fragrance like the finest musk on the face of the earth. Then they ascend and they do not pass by any group of angels but they say, ‘Who is this good soul?’ and they say, ‘It is so and so, the son of so and so, calling him by the best names by which he was known in this world, until they reach the lowest heaven. They ask for it to be opened to them and it is opened, and (the soul) is welcomed and accompanied to the next heaven by those who are closest to Allah, until they reach the seventh heaven. Then Allah Says: ‘Record the book of My slave in ‘Illiyeen (the seventh heaven), and return him to the earth, for from it I created them, to it I will return them and from it I will bring them forth once again.’ So his soul is returned to his body and there come to him two angels who make him sit up and they say to him, ‘Who is your Lord?’ He says, ‘Allah.’ They say, ‘What is your religion?’ He says, ‘My religion is Islam.’ They say, ‘Who is this man who was sent among you?’ He says, ‘He is the Messenger of Allah .’ They say, ‘What did you do?’ He says, ‘I read the Book of Allah and I believed in it.’ Then a voice calls out from heaven, ‘My slave has spoken the truth, so prepare for him a bed from Paradise and clothe him from Paradise, and open for him a gate to Paradise.’ Then there comes to him some of its fragrance, and his grave is made wide, as far as he can see. Then there comes to him a man with a handsome face and handsome clothes, and a good fragrance, who says, ‘Receive the glad tidings that will bring you joy this day.’ He says, ‘Who are you? Your face is a face which brings glad tidings.’ He says, ‘I am your righteous deeds.’ He says, ‘O Lord, hasten the Hour so that I may return to my family and my wealth.’ But when the disbelieving slave is about to depart this world and enter the Hereafter, there come down to him from heaven angels with black faces, bringing sackcloth, and they sit around him as far as the eye can see. Then the Angel of Death comes and sits by his head, and he says, ‘O evil soul, come forth to the wrath of Allah and His anger.’ Then his soul disperses inside his body, and then comes out cutting the veins and nerves, like a skewer passing through wet wool. When he seizes it, they do not leave it in his hand for an instant before they take it and put it in that sackcloth, and there comes from it a stench like the foulest stench of a dead body on the face of the earth. Then they ascend and they do not pass by any group of angels but they say, ‘Who is this evil soul?’ and they say, ‘It is so and so the son of so and so, calling him by the worst names by which he was known in this world, until they reach the lowest heaven. They ask for it to be opened to them and it is not opened.” Then the Messenger of Allah recited Allah's saying (which means): “The gates of Heaven will not be opened for them, nor will they enter Paradise until a camel enters into the eye of a needle [i.e. never]” [Quran 7:40]

He said: “Then Allah Says, ‘Record the book of My slave in Sijjeen (in the lowest earth), and return him to the earth, for from it I created them, to it I will return them and from it I will bring them forth once again.’ So his soul is cast down.” Then the Messenger of Allah recited the verse (which means): “ And he who associates with Allah — it is as though he had fallen from the sky and was snatched by the birds or the wind carried him down into a remote place.” [Quran 22:31]

He said: “Then his soul is returned to his body, and there come to him two angels who make him sit up and they say to him, ‘Who is your Lord?’ He says, ‘Oh, oh, I don’t know.’ They say, ‘What is your religion?’ He says, ‘Oh, oh, I don’t know.’ Then a voice calls out from heaven, ‘Prepare for him a bed from Hell and clothe him from Hell, and open for him a gate to Hell.’ Then there comes to him some of its heat and hot winds, and his grave is constricted and compresses him until his ribs interlock. Then there comes to him a man with an ugly face, ugly clothes, and a foul stench, who says, ‘Receive the bad news, this is the day that you were promised.’ He says, ‘Who are you? Your face is a face which forebodes evil.’ He says, ‘I am your evil deeds.’ He says, ‘O Lord, do not let the Hour come, do not let the Hour come.’” [Abu Dawood]