But they shall not go in to see when the holy things are covered, lest they die. When the holy things are covered - Literally, כבלע keballa, when they are swallowed down; which shows the promptitude with which every thing belonging to the holy of holies was put out of sight, for these mysteries must ever be treated with the deepest reverence; and indeed without this they could not have been to them the representatives of heavenly realities. See the concluding note Numbers 4:36 (note).
Related Commentaries of Numbers 4:20
Numbers 4:20
20 But they shall not go in to see when the holy things are covered, lest they die.