What is the ruling on praying behind an Imam who says "Allahu Akbar" or "Sami'allahu liman hamidah" after rising from prostration, considering that saying "Allahu Akbar" during the rising from prostration is obligatory, and is it necessary to repeat past prayers?

The Imam's saying "Allahu Akbar" (God is Greatest) after rising from prostration, and his saying "Sami'a Allahu liman hamidah" (Allah hears the one who praises Him) after rising from bowing, does not invalidate the prayer of the Imam or the prayer of the congregants. This is because the takbirat al-intiqal (transitionary takbirs) and tasmi' (saying "Sami'a Allahu liman hamidah") are considered sunnah (recommended) by the majority of scholars, not obligatory. Therefore, there is no need to repeat past prayers.