In the hadith of Sayyiduna Abu Hurayrah (may Allah be pleased with him) about the incident of the man who entered (the mosque) and prayed, and then said to the Prophet (peace and blessings be upon him): "By the One who sent you with the truth! I cannot pray any better than this, so teach me." So he (peace and blessings be upon him) said: "When you stand for prayer, say the takbir." Then he mentioned the complete hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / Q2268