Salawat: The Secret Key to Accepted Du'a

Hawzah News Agency- Imam Sadiq(pbuh) said:

مَن كانَت لَهُ حاجَةٌ إلى اللّه ِ عزّ و جلّ فَلْيَبدَأ بِالصَّلاةِ عَلى مُحَمَّدٍ و آلِهِ ، ثُمَّ يَسألْ حاجَتَهُ ، ثُمَّ يَختِمْ بِالصَّلاةِ عَلى مُحَمَّدٍ و آلِ مُحَمَّدٍ ، فإنَّ اللّه َ عزّ و جلّ أكرَمُ مِن أن يَقبَلَ الطَّرَفَينِ و يَدَعَ الوَسَطَ إذ كانَتِ الصَّلاةُ عَلى مُحَمَّدٍ و آلِ مُحَمَّدٍ لا تُحجَبُ عَنهُ .

Whoever has a need from Allah, the Almighty, should begin with sending blessings (salawat) upon Muhammad and his family,
then ask for his need, and then conclude with blessings upon Muhammad and the family of Muhammad. For Allah is too generous to accept the two ends (the salawat) and leave the middle (the supplication) unanswered — since blessings upon Muhammad and his family are never veiled from Him.

Usul al-Kafi, vol. 2, p. 494, h. 16