Hisnul Muslim · Dua 223 of 267
The excellence of asking for Allah's blessings upon the Prophet pbuh
وَقَالَ صلى الله عليه وسلم: ((مَا مِنْ أَحَدٍ يُسَلِّمُ عَلَيَّ إِلاَّ رَدَّ اللَّهُ عَلَيَّ رُوحِيَ حَتَّى أَرُدَّ عَلَيْهِ السَّلاَمَ)).
English meaning
The Prophet [PBUH] said: 'No one sends greetings (or prayers of peace) upon me but Allah returns my soul to me so that I may return his greetings