The Ultimate Question of Destiny:

Asma bint Abi Bakr (may Allah be pleased with her) reported that once at the time of Eclipse, the Messenger of Allah (may peace and blessings of Allah be upon him and his family) performed a long Eclipse prayer, then praised and glorified Allah (swt) and said,
“There was no such a thing as I did not see earlier but I have seen it just now at this place of mine, including Paradise and Hell. It was also revealed to me that you will be put in trials in your graves, and those trials will be like the trials of Masih-ad-Dajjal. You will be asked, “What do you know about this man”? (the Prophet). If the person is a believer, he would say, “He is Muhammad (may peace and blessings of Allah be upon him), the Messenger of Allah, who had come to us with clear evidences and guidance, so we accepted his teachings and followed him. And he is Muhammad, and he will repeat it thrice. Then the angels will say to him, “Sleep in peace as we have come to know that you were a faithful believer”. On the other hand, a hypocrite or a doubtful person will reply, ‘I do not know, but I heard people saying something and so I said the same”.

[Sahih Bukhari – Kitab-ul-Ilm]
[Sahih Muslim – Kitab-us-Salah]

Anas bin Malik (may Allah be pleased with him) reported that,

The Prophet (may peace and blessings of Allah be upon him) said, “When a human being is placed in his grave and his companions return and he even hears their foot steps, two angels come to him and make him sit and ask him: ‘What DID you use to say about this man Muhammad (in your lifetime)? If he is a believer, he would say: ‘I testify that he is Allah’s servant and His Messenger’. Then it will be said to him, ‘Look at your place in the Hell-Fire. Allah has CHANGED this (place of yours) with a place in Paradise’. Allah’s Messenger (may peace and blessings of Allah be upon him) said: “He would be shown both the places”. Qatada (may Allah be pleased with him) said: ‘It was mentioned to us that his grave expands to seventy cubits and is full with greenery until the Day when they would be resurrected’.

[Sahih Bukhari – Kitab-ul-Janaa’iz]
[Sahih Muslim - Kitab-ul-Jannah]

It is said that to remain steadfast on the answer of this question, abundant salutation (Salat o Salam) on our beloved Prophet will help. Please keep on saying,,,

الهم صل وسلم وبارك على سيدناومولانا محمد عبدك ورسولك النبي الامي وعلى آله وصحبه اجمعين