1 Samuel 6:3

Send it not empty They answer directly to the question, first in general; that it must not be sent back without some offering. In any wise return him a trespass-offering As an acknowledgment that they had offended the God of Israel by bringing his ark from its proper place; for which they begged his pardon by this offering. Then ye shall be healed, &c. Le Clerc renders this sentence, Then if ye shall be healed, it shall be known, or manifest unto you, why his hand is not removed from you. And it is evident this is the meaning of the words. For these diviners were not sure whence these plagues came; but they thought in this way they should either be healed or know that the ark was not the cause of their sickness. It shall be known You shall understand what is hitherto doubtful, whether he is the author of these calamities, and why they are continued so long upon you.