*Dought & clear, - Why is the Prophet’s grave in his mosque even though it is forbidden to take graves as places of worship?.

The hadeeth says, "May Allaah curse the Jews, for they have taken the
graves of their Prophets as places of worship". So how come the grave
of the Prophet (peace and blessings of Allaah be upon him) is inside
his mosque in Madeenah?.
Praise be to Allaah.
The scholars have discussed this issue, in the past and more recently,
and they refuted those who quote the fact that the grave of the
Prophet(peace and blessings of Allaah be upon him) is inside his
mosque as evidence that it is permissible to take graves as places of
worship, or to include graves in mosques. We will quote the fatwas of
some of our prominent scholars, which discuss in detail the matter
raised in the question.
1 – Shaykh 'Abd al-'Azeez ibn Baaz (may Allaah have mercy on him) said:
There is a specious argument put forward by those who worship graves,
namely the fact that the grave of the Prophet(peace and blessings of
Allaah be upon him) is in his mosque. The answer to that is that the
Sahaabah (may Allaah be pleased with them) did not bury him in his
mosque, rather they buried him in the house of 'Aa'ishah (may Allaah
be pleased with her). When al-Waleed ibn 'Abd al-Malik expanded the
Mosque of the Prophet(peace and blessings of Allaah be upon him) at
the end of the first century, he incorporated the room into the
mosque, but he did wrong thereby, and some of the scholars denounced
him for that, but he believed that there was nothing wrong with it for
the sake of expanding the mosque.
It is not permissible for a Muslim to take that as evidence that
mosques may be built over graves, or that people may be buried inside
mosques, because that goes against the saheeh ahaadeeth, and because
it is a means that may lead to shirk by associating the occupants of
the graves in worship with Allaah. End quote.
Majmoo' Fataawa al-Shaykh Ibn Baaz, 5/388, 389.
2 – Shaykh Muhammad ibn Saalih al-'Uthaymeen (may Allaah have mercy on
him) was asked about the ruling on praying in a mosque in which there
is a grave.
He replied:
Praying in a mosque in which there is a grave falls into two categories:
(i)Either the grave was there before the mosque, and the mosque was
built over the grave. It is essential to shun this mosque and not pray
therein, and the one who built it must knock it down; if he does not
do so, then the Muslim authorities must knock it down.
(ii)Or the mosque was there before the grave, and the deceased was
buried after the mosque was built. In the case the grave must be dug
up, and the remains taken out and buried with the people (in the
graveyard).
As for praying in such a mosque, it is permissible so long as the
grave is not in front of the worshipper, because the Prophet(peace and
blessings of Allaah be upon him) forbade praying in the direction of
graves.
With regard to the grave of the Prophet(peace and blessings of Allaah
be upon him) which is incorporated into his mosque, it is well known
that the Mosque of the Prophet(peace and blessings of Allaah be upon
him) was built before his death, and was not built over his grave. It
is also well known that the Prophet(peace and blessings of Allaah be
upon him) was not buried in the mosque, rather he was buried in his
house which was separate from the mosque. At the time of al-Waleed ibn
'Abd al-Malik he wrote to his governor in Madeenah, who was 'Umar ibn
'Abd al-'Azeez, in 88 AH, ordering him to dismantle the Prophet's
Mosque and add to it the rooms of the wives of the Prophet(peace and
blessings of Allaah be upon him). 'Umar gathered the prominent people
and fuqaha', and read the letter of the caliph al-Waleed to them. That
caused them distress, and they said: "Leave it as it is, that is
better." And it was narrated that Sa'eed ibn al-Musayyib denounced the
incorporation of 'Aa'ishah's room into the mosque, as if he feared
that the grave would be taken as a place of worship.
Umar wrote a letter to that effect to al-Waleed, and al-Waleed sent
word to him ordering him to carry out his instructions, so 'Umar had
no other choice. So you see that the grave of the Prophet(peace and
blessings of Allaah be upon him) was not placed in the mosque, and the
mosque was not built over it, so there are no grounds for those who
try to quote this as evidence that people may be buried inside mosques
or that mosques may be built over graves.
It is proven that the Prophet(peace and blessings of Allaah be upon
him) said: "May the curse of Allaah be upon the Jews and the
Christians; they have taken the graves of their Prophets as places of
worship." He said that as he was dying, as a warning to his ummah
against doing what they did. When Umm Salamah told him of a church
that she had seen in Ethiopia and the images therein, he said: "Those
people, if a righteous man among them died, they would build a place
of worship over his grave. They are the most evil of people before
Allaah." And it was narrated from Ibn Mas'ood (may Allaah be pleased
with him) that the Prophet(peace and blessings of Allaah be upon him)
said: "Among the most evil of people upon whom the Hour will come when
they are still alive are those who take graves as places of worship."
Narrated by Imam Ahmad with a jayyid isnaad.
The believer should not accept to follow the ways of the Jews and the
Christians, or to be among the most evil of people.
Majmoo' Fataawa al-Shaykh Ibn 'Uthaymeen, 12/question no. 292
And Allaah knows best.