When the Prophet ﷺ would open the prayer, he would say the takbir, then say, "Truly my prayer, my rites of worship, my life, and my death belong to Allah, Lord of the worlds, who has no partner. With this I have been commanded, and I am among the Muslims. Allah, guide me to the best of deeds and the best of character, for none guides to the best of them except You, and protect me from evil deeds and evil character, for none protects from their evil except You."
أخبرنا عمرو بن عثمان بن سعيد قال حدثنا شريح بن يزيد الحضرمي قال أخبرني شعيب بن أبي حمزة قال أخبرني محمد بن المنكدر
كان النبي ﷺ إذا استفتح الصلاة كبر ثم قال إن صلاتي ونسكي ومحياي ومماتي لله رب العالمين لا شريك له وبذلك أمرت وأنا من المسلمين اللهم اهدني لأحسن الأعمال وأحسن الأخلاق لا يهدي لأحسنها إلا أنت وقني سيئ الأعمال وسيئ الأخلاق لا يقي سيئها إلا أنت
[Its chain of transmission is sahih] Tabarani narrated it in Musnad Shamiyin, 149/4, 150, no. 2974, from the hadith of Amr bin Uthman, who is the son of Kathir bin Dinar, al-Himsi, through the same chain. It is also found in Kubra, no. 970, and the following hadith serves as a corroborating witness for it.