Ether 9:33

And it came to pass that the Lord did cause the serpents that they should pursue them no more, but that they should hedge up the way, that the people could not pass; that whoso should attempt to pass, might fall by the poisonous serpents.

The Lord made the snakes stop chasing them. Instead, the snakes blocked the way so the people could not pass. Anyone who tried to pass would die from the poisonous snakes.

The Lord stopped the serpents from chasing them further. Instead, he made the snakes block the way so no one could pass. Anyone who tried would be killed by the poisonous serpents.