Must the prayer be repeated if the worshiper, out of ignorance, added a second declaration of faith after the prayer?

The prayer is valid if the questioner recited the tashahhud with a reported wording, such as the tashahhud of Ibn Mas'ud, for everything authentically reported from the Prophet (peace be upon him) is permissible. As for adding "I bear witness that there is no god but Allah, and that Muhammad is the Messenger of Allah" to the tashahhud, it does not invalidate the prayer. The same applies if the supplication after the tashahhud is not recited in order, for supplication is commendable (mustahabb) and not obligatory (wajib), and the prayer is valid without it.