(صَلِّ (صَلَّى / اَلصَّلَاةُ عَلى النَّبِي
O Allah, have mercy upon Muhammad and praise him in the lofty assembly i.e. amongst the elite angels who are close to Allah.
(سَلِّم (سَلَّمَ/ اَلسَّلَامُ على النَّبِيِّ
O Allah, send peace upon Muhammad; protect him, keep him safe from harm and take care him.
Thus, salāh is the acquisition of all good and salām is the protection from all evil.
An Explanation of the Salah Ibrahimiyyah
اَللّٰهُمَّ صَلِّ عَلَىٰ مُحَمَّدٍ وَعَلَىٰ آلِ مُحَمَّدٍ ، كَمَا صَلَّيْتَ عَلَىٰ إِبْرَاهِيْمَ وَعَلَىٰ آلِ إِبْرَاهِيْمَ ، إِنَّكَ حَمِيْدٌ مَّجِيْدٌ ، اَللّٰهُمَّ بَارِكْ عَلَىٰ مُحَمَّدٍ وَعَلَىٰ آلِ مُحَمَّدٍ ، كَمَا بَارَكْتَ عَلَىٰ إِبْرَاهِيْمَ وَعَلَىٰ آلِ إِبْرَاهِيْمَ ، إِنَّكَ حَمِيْدٌ مَّجِيْدٌ
O Allah, honour and have mercy upon Muḥammad and the family of Muḥammad as You have honoured and had mercy upon Ibrāhīm and the family of Ibrāhīm: indeed, You are the Most Praiseworthy, the Most Glorious. O Allah, bless Muḥammad and the family of Muḥammad as You have blessed Ibrāhīm and the family of Ibrāhīm: indeed, You are the Most Praiseworthy, the Most
اَللّٰهُمَّ صَلِّ [O Allah, honour and have mercy]: O Allah, have mercy upon Muḥammad and praise him in the lofty assembly. The ‘lofty assembly’ refers to the elite angels who are close to Allah (subḥānahū wa taʿālā).
Salāh also means ‘honour him’ i.e. honour him in the world by elevating his mention, granting victory to his dīn and preserving his sharī‘ah; and honour him in the hereafter by rewarding him abundantly, accepting his intercession on behalf of his ummah and granting him the loftiest station of glory (maqām mahmūd). (Ibn Hajar quoting Halīmī in Fath al-Bārī)
وَعَلَىٰ آلِ مُحَمَّدٍ [And upon the family of Muḥammad ﷺ]: This phrase could be a reference to: (1) His family (2) His followers. By invoking ṣalāh on his followers, you are honouring the Messenger g by honouring those who are dear to him.
بَارِكْ [Bless]: Bārik is derived from barakah, and linguistically has two meanings: (1) to be firm and continuous and (2) to grow and increase. Thus, it is similar to stating, “O Allah continue to bless and honour Muḥammad ﷺ and his followers. Increase him and his followers in every form of good. Bless him in the mission that he came with and make his legacy universal.”
حَمِيْدٌ [The Most Praiseworthy]: Allah (subḥānahū wa taʿālā) is worthy of all praise in His Essence, His Attributes and His Actions. He also praises His praiseworthy slaves. One of His greatest blessings is that He allowed His creation to praise Him.
مَّجِيْدٌ [The Most Glorious]: His glory and greatness know no ends. He is the Most Generous and bestows endless favours. He is Noble and Exalted. The glory of Allah (subḥānahū wa taʿālā) refers to His beautiful actions combined with nobility.