In a coffer by the side thereof They had either heard, or by their present sufferings were made to fear, that it was dangerous to look into the ark; and therefore they did not open it to put their present within it.
Related Commentaries of 1 Samuel 6:8
1 Samuel 6:8
8 And take the ark of the LORD, and lay it upon the cart; and put the jewels of gold, which ye return him for a trespass offering, in a coffer by the side thereof; and send it away, that it may go.