If a mezuzah is checked and found invalid, may the invalid mezuzah be put back until a valid one is purchased?

This source-based Torah study examines the question: If a mezuzah is checked and found invalid, may the invalid mezuzah be put back until a valid one is purchased? The canonical Hebrew discussion develops the issue through the weekly Torah portion and the sources cited there, preserving the distinctions, tensions, and practical implications of the original text. This localized discovery layer does not add any new halakhic, medical, legal, scientific, historical, theological, or empirical ruling or claim beyond the canonical Hebrew source.