"The Messenger of Allah (ﷺ) used to say the takbir every time he got up, went down, stood and sat. Abu Bakr, 'Umar, and 'Uthman (did likewise)."
Sunan an-Nasa'i Book 12, Hadith 121
← Previous Hadith "In the prayer of the Messenger of Allah (ﷺ), his bowing, his prostration, standing after he raised his head from bowing and (sitting) between the two prostrations, were almost the same."

Sunan an-Nasa'i Book 12, Hadith 120 Next Hadith → "When the Messenger of Allah (ﷺ) stood to pray, he said the takbir, when he (started), then he said the takbir when he bowed, then he said: 'Sami Allahu liman hamidah (Allah hears the one who praises Him)', when he stood up from bowing. Then he said when he was standing: 'Rabbana lakal-hamd.' Then he said the takbir when he went down in prostration, then he said the takbir when he raised his head, and he did that throughout the entire prayer until he finished it, and he said the takbir when he stood up after the first two rak'ahs, after sitting."

Sunan an-Nasa'i Book 12, Hadith 122