What is the ruling on someone who makes a mistake in congregational prayer by adding an extra rak'ah or prostrating before bowing (ruku'), then realizes their error and completes their prayer? Is it obligatory for them to repeat the prayer, or is it permissible for them to interrupt it and restart it as one who joins the prayer late (masbuq)?

If the congregant errs, such as standing during the first tashahhud or prostrating after standing and before bowing, he should correct his mistake, and his prayer is not invalidated by that. He is not required to perform the sujood of forgetfulness nor to repeat the prayer. However, it is not permissible to break the prayer in order to restart it.