Reported by Thauban رضي الله عنه : Whenever the Messenger of Allah صلى الله عليه وسلم finished his Salat (prayer), he would beg forgiveness three times [by saying, `Astaghfirullah’ (3 times)] and then he would say:
Allāhumma antas-salāmu, wa minkas-salāmu, tabarakta ya dhal-jalali wal-ikram.
O Allah! you are the bestower of security and security comes from you; blessed are you. O Possessor of glory and honour