What is the ruling on the prayer of one who completes the word "akbar" when already close to prostration or actually prostrating, or who errs in pronouncing "Allahu akbar" by replacing the letter "ra" with "lam" or by saying "Allahu wa kabbar" while prostrating or sitting for the Tashahhud? And is it obligatory to repeat the prayer or only the takbir, knowing that the takbirat of transition are a sunnah according to the Shafi'i school?

The prescribed (Sunnah) way is for the takbirat of transition to be said during the transition itself, not before or after it. If you complete the takbir before reaching the position (rukn), your prayer is valid by consensus. If some of the takbir occurs after the transition, your prayer is valid according to the preponderant opinion of the Hanbalis (who consider the takbir obligatory); as for the majority of scholars, the takbir is a Sunnah (recommended) and the prayer is valid in all cases.

If you make a mistake in the takbir: - If it is possible to correct it before the transition: You must say the takbir again. - If you have already settled into the position: The time for the takbir has passed, and it is not prescribed to say it. There is nothing upon you according to the majority of scholars. However, the Hanbalis require the prostration of forgetfulness (sujud al-sahw), and a mistake in the takbir is treated like forgetting or ignorance, so it does not invalidate the prayer.

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