In the Name of Allah, the Gracious, the Merciful
Imam al-Nawawi records in his book Meadows of the Righteous:
باب الأمر بالصلاة عَلَيْهِ وفضلها وبعض صيغها
Chapter on the command to send blessings upon the Prophet, its virtues, and its formulations.
Source: Riyāḍ al-Ṣāliḥīn 1/387
Allah Almighty said:
إِنَّ اللَّهَ وَمَلَائِكَتَهُ يُصَلُّونَ عَلَى النَّبِيِّ يَا أَيُّهَا الَّذِينَ آمَنُوا صَلُّوا عَلَيْهِ وَسَلِّمُوا تَسْلِيمًا
Indeed, Allah showers His blessings upon the Prophet, and His angels pray for him. O believers! Invoke Allah’s blessings upon him, and salute him with worthy greetings of peace.
Surat al-Ahzab 33:56
Abdullah ibn Amr reported: The Prophet, peace and blessings be upon him, said:
مَنْ صَلَّى عَلَيَّ وَاحِدَةً صَلَّى اللَّهُ عَلَيْهِ عَشْرًا
Whoever sends blessings upon me once, Allah will send blessings upon him ten times.
Source: Ṣaḥīḥ Muslim 408, Grade: Sahih
Ibn Mas’ud reported: The Messenger of Allah, peace and blessings be upon him, said:
أَوْلَى النَّاسِ بِي يَوْمَ الْقِيَامَةِ أَكْثَرُهُمْ عَلَيَّ صَلَاةً
The closest of people to me on the Day of Resurrection are those who sent the most blessings upon me.
Source: Sunan al-Tirmidhī 484, Grade: Hasan
Aws ibn Aws reported: The Messenger of Allah, peace and blessings be upon him, said:
إِنَّ مِنْ أَفْضَلِ أَيَّامِكُمْ يَوْمَ الْجُمُعَةِ فِيهِ خُلِقَ آدَمُ وَفِيهِ قُبِضَ وَفِيهِ النَّفْخَةُ وَفِيهِ الصَّعْقَةُ فَأَكْثِرُوا عَلَيَّ مِنْ الصَّلَاةِ فِيهِ فَإِنَّ صَلَاتَكُمْ مَعْرُوضَةٌ عَلَيَّ
Verily, the best of your days is Friday. Adam was created on it, he died on it, the Trumpet will be blown on it, and the Shout will be made on it. Thus, send blessings upon me often, for your blessings are presented to me.
Source: Sunan Abī Dāwūd 1047, Grade: Sahih
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
رَغِمَ أَنْفُ رَجُلٍ ذُكِرْتُ عِنْدَهُ فَلَمْ يُصَلِّ عَلَيَّ
May he be humbled in whose presence I am mentioned, but he does not send blessings upon me.
Source: Sunan al-Tirmidhī 3545, Grade: Sahih
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
لاَ تَجْعَلُوا بُيُوتَكُمْ قُبُورًا وَلاَ تَجْعَلُوا قَبْرِي عِيدًا وَصَلُّوا عَلَىَّ فَإِنَّ صَلاَتَكُمْ تَبْلُغُنِي حَيْثُ كُنْتُمْ
Do not turn your houses into graves, and do not turn my grave into a place of festivity. Send blessings upon me, for your blessings will reach me wherever you are.
Source: Sunan Abī Dāwūd 2042, Grade: Sahih li ghayrihi
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
مَا مِنْ أَحَدٍ يُسَلِّمُ عَلَيَّ يعني عند قبره إِلَّا رَدَّ اللَّهُ عَلَيَّ رُوحِي حَتَّى أَرُدَّ عَلَيْهِ السَّلَامَ
None of you greets me with peace (at his grave) except Allah returns my spirit, that I may return his greeting of peace.
Source: Sunan Abī Dāwūd 2041, Grade: Sahih
Ali ibn Abu Talib reported: The Prophet, peace and blessings be upon him, said:
الْبَخِيلُ الَّذِي مَنْ ذُكِرْتُ عِنْدَهُ فَلَمْ يُصَلِّ عَلَيَّ
The miser is one in whose presence I am mentioned, but he does not send blessings upon me.
Source: Sunan al-Tirmidhī 3546, Grade: Sahih
Fadalah ibn ‘Ubayd reported: The Prophet, peace and blessings be upon him, heard a man supplicating in his prayer, and he did not send blessing upon him. The Prophet said:
عَجِلَ هَذَا
This man has rushed.
Then, the Prophet called for the man, saying:
إِذَا صَلَّى أَحَدُكُمْ فَلْيَبْدَأْ بِتَمْجِيدِ رَبِّهِ جَلَّ وَعَزَّ وَالثَّنَاءِ عَلَيْهِ ثُمَّ يُصَلِّي عَلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ثُمَّ يَدْعُو بَعْدُ بِمَا شَاءَ
When one of you prays, let him begin by praising and thanking Allah, then let him send blessings upon the Prophet, then let him supplicate for whatever he wishes.
Source: Sunan al-Tirmidhī 3477, Grade: Sahih
Ka’b ibn ‘Urjah reported: We asked, “O Messenger of Allah, how do we send blessings upon you and the people of the house? Allah has taught us how to send peace upon you.” The Prophet, peace and blessings be upon him, said:
قُولُوا اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا صَلَّيْتَ عَلَى إِبْرَاهِيمَ وَعَلَى آلِ إِبْرَاهِيمَ إِنَّكَ حَمِيدٌ مَجِيدٌ اللَّهُمَّ بَارِكْ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا بَارَكْتَ عَلَى إِبْرَاهِيمَ وَعَلَى آلِ إِبْرَاهِيمَ إِنَّكَ حَمِيدٌ مَجِيدٌ
Say, ‘O Allah, send grace upon Muhammad and the house of Muhammad, just as You have sent grace upon Abraham and the house of Abraham. Verily, You are Praiseworthy and Majestic. O Allah, bless Muhammad and the house of Muhammad, just as You have blessed Abraham and the house of Abraham. Verily, You are Praiseworthy and Majestic.’
Source: Ṣaḥīḥ al-Bukhārī 3370, Grade: Muttafaqun Alayhi
In another narration, the Prophet said:
قُولُوا اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا صَلَّيْتَ عَلَى آلِ إِبْرَاهِيمَ وَبَارِكْ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا بَارَكْتَ عَلَى آلِ إِبْرَاهِيمَ فِي الْعَالَمِينَ إِنَّكَ حَمِيدٌ مَجِيدٌ
Say, ‘O Allah, send grace upon Muhammad and the house of Muhammad, just as You have sent grace upon the house of Abraham. Verily, You are Praiseworthy and Majestic. And bless Muhammad and the house of Muhammad, just as You have blessed the house of Abraham among the worlds. Verily, You are Praiseworthy and Majestic.’
Source: Ṣaḥīḥ Muslim 405, Grade: Sahih
And in another narration, the Prophet said:
قُولُوا اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلَى أَزْوَاجِهِ وَذُرِّيَّتِهِ كَمَا صَلَّيْتَ عَلَى آلِ إِبْرَاهِيمَ وَبَارِكْ عَلَى مُحَمَّدٍ وَعَلَى أَزْوَاجِهِ وَذُرِّيَّتِهِ كَمَا بَارَكْتَ عَلَى آلِ إِبْرَاهِيمَ إِنَّكَ حَمِيدٌ مَجِيدٌ
Say, ‘O Allah, send grace upon Muhammad, his wives, and his progeny, just as You have sent grace upon the house of Abraham. And bless Muhammad, his wives, and his progeny, just as You have blessed the house of Abraham. Verily, You are Praiseworthy and Majestic.’
Source: Sahih Muslim 407, Grade: Sahih
Success comes from Allah, and Allah knows best.