Say three times:
رَضِيتُ بِاللَّهِ رَبًّا، وَبِالْإِسْلاَمِ دِينًا وَبِمُحَمَّدٍ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ نَبِيًّا
I am pleased with Allaah as a Lord, and Islaam as a religion and Muhammad as a Prophet.
Radheetu billaahi Rabban, wa bil-'Islaami deenan, wa bi-Muhammadin (sallallaahu 'alayhi wa sallama) Nabiyyan.
Allah has promised that anyone who says every morning or evening will be pleased on the Day of Resurrection.
Ahmad 4/ 337, An-Nasa'i, Ibn As-Sunni (no. 68), At-Tirmizi 5/465.