Hazrat Hasan Basri رحمه الله mentioned, “Whoever wishes to drink from the Howdh-e-Kawthar of Mustafa صلي الله عليه وسلم with the cup of full measure, then he should recite the following Durood:
أللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلَى آلِهِ وَأَصْحَابِهِ وَأَوْلَادِهِ وَأَزْوَاجِهِ وَذُرِّيَّتِهِ وَأَهْلِ بَيْتِهِ وَأَصْهَارِهِ وَأَنْصَارِهِ وَأَشْيَاعِهِ وَمُحِبّيْهِ وَأُمَّتِهِ وَعَلَيْنَا مَعَهُمْ أَجْمَعِيْنَ يَا أَرْحَمَ الرَّاحِمِينَ
O Allah! Send salutations upon Muhammad صلي الله عليه وسلم, his family, his Sahabah, his children, his wives, his progeny, his household, his relatives through marriage, his helpers (the Ansaar رضي الله عنهم ), his followers, those who love him, his Ummah, and upon us all with them, O Most Merciful of those who show mercy.
(The Gift of Durood and Salam pg.116)