Why are blessings recited immediately before performing a mitzvah without concern that something may prevent its completion?

This Torah study examines the question: Why are blessings recited immediately before performing a mitzvah without concern that something may prevent its completion? The canonical Hebrew discussion develops the issue through the weekly Torah portion and the sources cited there, preserving the distinctions, tensions and practical implications that belong to the source itself. This localized layer is designed for study and discovery; it does not add a new halakhic, medical, legal, historical or empirical ruling beyond the canonical Hebrew source.