Praise be to Allah.
What is meant by invoking blessings in this hadith is offering supplication (du‘aa’) asking for forgiveness and mercy for them, and for admission to paradise and salvation from hell, and so on – as in the verse in which Allah, may He be glorified and exalted, says (interpretation of the meaning): “Take, [O, Muhammad], from their wealth a charity by which you purify them and cause them increase, and invoke [ Allah 's blessings] upon them. Indeed, your invocations are reassurance for them. And Allah is Hearing and Knowing” [at-Tawbah 9:103]. This refers to supplication (du‘aa’).
And Allah is the source of strength. May Allah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote.
Permanent Committee for Academic Research and Iftaa’
Shaykh ‘Abd al-‘Azeez ibn ‘Abdillah ibn Baaz, Shaykh ‘Abd ar-Razzaaq ‘Afeefi, Shaykh ‘Abdullah ibn Ghadyaan, Shaykh ‘Abdullah ibn Qa‘ood
Fataawa al-Lajnah ad-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Iftaa’ (24/219)