Surah No. 33, Al Ahzaab, Ayat No. 56
إِنَّ اللَّهَ وَمَلَائِكَتَهُ يُصَلُّونَ عَلَى النَّبِيِّ يَا أَيُّهَا الَّذِينَ آمَنُوا صَلُّوا عَلَيْهِ وَسَلِّمُوا
This Ayat can be linked to the action of three people, One from Allah, the second from the Angels and the third from the Believers.
1. Allah : Salat from Allah means He Praises the Apostle, showers His blessings, is very kind to him, blesses his work, exalts his name, and showers His mercies on him and keeps his name high.
2. Angels : Salat from the Angels means, they extend tremendous Love to the Apostle and pray to Allah that He shall cause the religion and Shari'ah to flourish and exalt him to the laudable position and raise the Prophet to the great heights of Muqaame Mehmood.
3. Believers : The Prophet has established a new civilzation, new culture and an organised system of life for the followers. In his mission he had to receive brutal treatment and his companions were severly tortured by the non believers in Mecca. The amount of resistance and difficulties he had faced were incomparable. He had created a smooth path for the followers to lead such a life so that they all can get a good reward in the Hereafter. For such a Grand Personality Allah has decreed two things for the followers :
( i ) صَلُّوا عَلَيْهِ ( Sallu Alaihe )
( ii ) وَسَلِّمُوا تَسْلِيمًا ( Sallemu Taslima )
For Sallu Alaihe, the followers must love the Prophet, praise him and seek Allah's blessings for him.
For Sallemu Taslima, the followers must pray for his peace and must follow the guidelines practiced by Prophet Mohammad (saws).
When his companions asked the prophet that what are the methods of saluting you (Salam), seeking Allah's Blessings on you and salat on you. He replied :
( a ) When you recite salat (Namaz) and in every second rakat you recite Attahiyyat and during reciting Attahiyyat you recite Assalamo alaika ya ayyohan Nabiyyo wa Rahmatullahe wa Barakatohu, here you are saluting the Prophet and also seeking Allah's Blessings for him.
( b ) For sending salat on him the Prophet had taught both the darood and asked the followers to recite them at the end of the each salat (namaz). Apart from this the darood should be recited when you hear the name of the Prophet. The darood can also be recited at any other time.
[ Ref : Tafhimul Quran,Vol. V, Tafsir Surah Al Ahzab ]
Whenever you make supplication (dua ) after your Salat , if you recite darood at the begining and at the end of the dua, the acceptibility percentage of the dua goes up.
[ Ref : Tarjuma Quran by Maulana Abdul Karim Parekh of Nagpur, India ]