All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.

Invoking blessings upon the Prophet (Peace and blessings be upon him) is a sublime Dhikr that a Muslim performs following the order of Allah Who said {What means}: "God and His angels send blessings on the Prophet: O ye that believe! Send ye blessings on him, and salute him with all respect." {Al-Ahzab,56}. It is recommended for a Muslim to write the expressions of blessings completely, be that in Arabic or any other language. This way he/she combines both prayer and peace, writes the expressions in full, such as (Peace and blessings be upon him) and (Prayer and peace be upon him), and utters them as well. Moreover, it is disliked for a Muslim to suffice with writing the abbreviations of sending blessings upon the Prophet (Peace be upon him); namely (PBUH) so long as writing the full expressions is possible.

An-Nawawi (May Allah have mercy on him) says: "A Muslim should be keen on writing the expressions of invoking blessings upon the Prophet (Peace be upon him) and never tire of repeating that since one who doesn`t do so loses a great reward. The same applies to expressions of praising Allah (Subhanahu wa Ta`ala), such as (Aza wa jall) and (Subhanahu wa Ta`ala), and the like. The same also applies to the expressions (May Allah be pleased with him) and (May Allah have mercy on him) when mentioning the companions, the scholars, and the rest of the righteous. However, it is disliked for a Muslim to use abbreviations of sending blessings upon the Prophet (Peace be upon him). Rather, he/she should write the expressions of blessings in full." {At-Takreeb wat-Taiseer, P.68}.

In conclusion, it is recommended to write and utter the complete expressions of invoking blessings upon the Prophet (Peace be upon him) and shouldn`t suffice with using abbreviations. However, one who has to write the abbreviations should at least utter the expressions in full. And Allah the Almighty knows best.