As per Qur'an:
Allah and His angels send blessings on the Prophet: O ye that believe! Send ye blessings on him, and salute him with all respect.
—Qur'an, Sura 33 (al-Ahzab)
ALLAHUMMA SALLI ALA MUHAMMADIW WA ALA AALI MUHAMMADIN KAMAA SALLAITA ALA IBRAHIMA WA ALA AALI IBRAHIMA INNAKA HAMIDUM MAJID.
ALLAHUMMA BAARIK ALA MUHAMMADIW WA ALA AALI MUHAMMADIN KAMAA BAARAKTA ALA IBRAHIMA WA ALA AALI IBRAHIMA INNAKA HAMIDUM MAJID.
“O Allah, let Your Blessings come upon Muhammad and the family of Muhammad, as you have blessed Ibrahim and his family. Truly, You are Praiseworthy and Glorious. Allah, bless Muhammad and the family of Muhammad, as you have blessed Ibrahim and his family. Truly, You are Praiseworthy and Glorious”.
Hadith
Anas ibn Malik narrates that Muhammad (S.A.W.W) said:
He who reads a single Durood upon me, Almighty Allah blesses him ten times, ten of his sins are forgiven, and he is increased ten times in stages.
The famous companion of the Prophet (sallal laahu alaihi wasallam), Hadrat Ka’ab bin Ujrah (radi Allahu anhu), narrates that once it was enquired from Sayyiduna Rasoolullah (sallal laahu alaihi wasallam) as to how blessings should be sent to him. The Prophet (sallal laahu alaihi wasallam) replied that the blessings be said in the manner (it has been mentioned) above, that is, Durood-e-Ibrahimi.