Must one make up prayers in which "Peace be upon us; peace be upon the righteous servants of Allah" was said instead of "Peace be upon us and upon the righteous servants of Allah" during the Tashahhud?

The Tashahhud is considered obligatory, and it is not permissible to omit any of its obligatory letters. However, if someone omitted something from it out of ignorance, they are not required to repeat the prayer, as some scholars permit acting upon a less preferred opinion after the act has occurred and its rectification would be difficult. Similarly, whoever omits a condition or a pillar out of ignorance is not obligated to repeat the prayer. Therefore, it is necessary to adhere to the correct form of the Tashahhud in the future, and there is no repetition required for what has passed.