Ibn al-Uthaymeen (may Allah have Mercy on him) said:
The combination of sending Peace and Blessings (in supplication)
upon the Prophet has a marvelling secret:
Blessings: the supplicant is asking for something to be
given to him - praise.
Peace: the supplicant is asking for something to be diverted
from him – harm.
Sharh al-Aqidah al-Wasitiyyah, 1/46