This excerpt is taken from Sheikh al-Islam Imam Ibn Taymiyyah's book Al-Jawab al-Bahir fi Zuwar al-Maqabir, translated by Sheikh Ataullah Saqib.
The Virtue and Method of Sending Blessings and Peace upon the Messenger
It is unanimously recommended to prepare for travel when performing acts of worship such as prayer, recitation of the Holy Quran, supplication, and I'tikaf in Masjid al-Nabawi and Masjid al-Aqsa. When a person enters Masjid al-Nabawi, it is necessary for him to send blessings and peace upon the Prophet Muhammad (peace be upon him) and also to recite blessings and peace upon him during the prayer because Allah Almighty says:
إِنَّ اللَّهَ وَمَلَائِكَتَهُ يُصَلُّونَ عَلَى النَّبِيِّ ۚ يَا أَيُّهَا الَّذِينَ آمَنُوا صَلُّوا عَلَيْهِ وَسَلِّمُوا تَسْلِيمًا ﴿٥٦﴾
"Indeed, Allah and His angels send blessings upon the Prophet. O you who have believed, ask [Allah to confer] blessing upon him and ask [Allah to grant him] peace."
Reference: (33-Al-Ahzab:56)
Whoever sends blessings and peace upon the Prophet Muhammad (peace be upon him) once, the Merciful Lord sends mercy upon him ten times.
Reference: Sahih Muslim, Book of Prayer: Chapter on Sending Blessings on the Prophet (Hadith: 408)
A true believer should pray for the attainment of the station of intercession for the Mercy to the Worlds (the Prophet Muhammad, peace be upon him). It is narrated in Sahih Muslim that the Prophet (peace be upon him) said:
إذا سمعتم المؤذن فقولوا مثل ما يقول ثم صلوا على فإنه من صلى على مرة صلى الله عليه عشرا ثم سلوا الله لي الوسيلة فإنها درجة فى الجنة لا تنبغي إلا لعبد من عباد الله وأرجو أن أكون أنا هو فمن سأل لي الوسيلة حلت له الشفاعة
"When you hear the Mu'adhdhin (caller to prayer) say the Adhan, say what he says, then send blessings upon me, for whoever sends blessings upon me once, Allah will send ten blessings upon him. Then ask Allah to grant me the 'Waseelah' (a station in Paradise), for it is a position in Paradise that will be granted to only one of Allah's servants, and I hope that I am that servant. Whoever prays for my Waseelah, my intercession will be obligatory for him."
Reference: Sahih Muslim, Book of Prayer: Chapter on Saying What the Mu'adhdhin Says (Hadith: 384)
Then send blessings upon me, for whoever sends blessings upon me once, Allah sends ten mercies upon him, then pray for my Waseelah. Because Waseelah is a rank among the degrees of Paradise that is exclusive to only one of Allah's servants, and I hope that servant is me. So whoever prays for my Waseelah, my intercession will become obligatory for him on the Day of Judgment."
The Prophet Muhammad (peace be upon him) said:
من قال حين يسمع النداء اللهم رب هذه الدعوة التامة والصلاة القائمة آت محمدا الوسيلة والفضيلة وابعثه مقاما محمودا الذى وعدته إنك لا تخلف الميعاد حلت له شفاعتي القيمه
"Whoever, after hearing the Adhan, prays this supplication: 'O Owner of this perfect call and established prayer! Grant Muhammad the Waseelah and the virtue and the praiseworthy station which You have promised him,' for You do not break Your promise, then my intercession will be permissible for him on the Day of Resurrection."
Reference: Sahih Bukhari, Book of Adhan: Chapter on Supplication at the Call (Hadith: 214)
It is obligatory to make the above supplication; also, it is permissible to greet the honored grave because in Sunan it is narrated that the Prophet (peace be upon him) said:
ما من أحد يسلم على إلا رد الله على روحي حتى أرد عليه السلام
"If anyone sends greetings upon me, Allah will return my soul to my body so that I may respond to his greeting."
Reference: Sunan Abi Dawood, Book of Pilgrimage: Chapter on Visiting Graves (Hadith: 2041)
Thus, from east to west, north to south, from any region of the world, when anyone sends blessings and peace upon the Messenger of Allah, the Merciful Lord conveys that blessing and peace to the Prophet Muhammad (peace be upon him). Accordingly, in Sunan, Aws ibn Aws (may Allah be pleased with him) narrates that the Prophet (peace be upon him) said:
أكثروا على من الصلاة يوم الجمعة وليلة الجمعة فإن صلاتكم معروضة على قالوا وكيف تعرض صلاتنا عليك وقد أرمت أى صرت رميما قال إن الله حرم على الأرض أن تأكل لحوم الأنبياء
"Send abundant blessings upon me on the night between Thursday and Friday and on Friday, for on that day your blessings are presented before me." The Companions (may Allah be pleased with them) asked, "How will our blessings be presented to you when you have been buried in the earth?" The Prophet (peace be upon him) replied, "Allah has forbidden the earth to consume the bodies of the Prophets."
Reference: Sunan Abi Dawood, Book of Prayer: Chapter on the Virtue of Friday and the Night of Friday (Hadith: 1047) Sunan an-Nasa'i, Book of Friday: Chapter on Increasing Prayer on the Prophet on Friday (Hadith: 1373) Sunan Ibn Majah, Book of Establishing Prayer: Chapter on the Virtue of Friday (Hadith: 1085)
For this reason, the Prophet Muhammad (peace be upon him) said:
لا تتخذوا قبري عيدا وصلوا على حيث ما كنتم فإن صلاتكم تبلغني
"Do not make my grave a place of festivity. Wherever you are, keep sending blessings upon me, for your blessings will reach me."
Reference: Sunan Abi Dawood, Book of Pilgrimage - Chapter on Visiting Graves (Hadith: 2042)
Blessings and peace upon the Prophet Muhammad (peace be upon him) reach him from afar just as they do from near. It is narrated in Sunan an-Nasa'i that the Prophet (peace be upon him) said:
إن لله ملائكة سياحين يبلغوني عن أمتي السلام
"Allah has appointed some special angels who roam the earth and convey the greetings of my Ummah to me."
Reference: Sunan an-Nasa'i, Book of Forgetfulness: Chapter on Greeting the Prophet (Hadith: 1283)
The Merciful Lord has commanded us to send blessings and peace upon the Messenger of Allah, and after praising Allah Almighty in every prayer, it is prescribed to recite this supplication:
السلام عليك أيها النبى ورحمة الله وبركاته
"O Prophet! May the peace, mercy, and blessings of Allah be upon you."
Reference: Sahih Bukhari, Book of Adhan: Chapter on the Final Tashahhud (Hadith: 831) Sahih Muslim, Book of Prayer: Chapter on Tashahhud in Prayer (Hadith: 402)
This blessing and peace reach the Messenger of Allah from east and west as well. When we want to send blessings and peace upon the Messenger of Allah, we should say:
اللهم صل على محمد وعلى آل محمد كما صليت على إبراهيم وعلى آل إبراهيم إنك حميد مجيد اللهم بارك على محمد وعلى آل محمد كما باركت على إبراهيم وعلى آل إبراهيم إنك حميد مجيد
"O Allah! Send Your mercy upon Muhammad and upon the family of Muhammad, as You sent Your mercy upon Ibrahim and upon the family of Ibrahim. Indeed, You are Praiseworthy and Glorious. O Allah! Send Your blessings upon Muhammad and upon the family of Muhammad, as You sent Your blessings upon Ibrahim and upon the family of Ibrahim. Indeed, You are Praiseworthy and Glorious."
Reference: Sahih Bukhari, Book of the Prophets' Hadiths: Chapter 10 (Hadith: 3370) Sahih Muslim, Book of Prayer: Chapter on Sending Blessings on the Prophet after Tashahhud (Hadith: 408)