That strengtheneth the spoiled against the strong, so that the spoiled shall come against the fortress.
Amos 5:9 belongs with a condemnation of religious leaders who turned justice aside and dealt cruelly with the righteous. Their conduct exposed the corruption that follows when God's law is rejected. In that setting the verse declares that God strengthens the spoiled and oppressed against the strong. By that divine strengthening the plundered are enabled to advance successfully against the fortress.
Amos 5:9 belongs with a condemnation of religious leaders who turned justice aside and dealt cruelly with the righteous. Their conduct exposed the corruption that follows when God's law is rejected. In that setting the verse declares that God strengthens the spoiled and oppressed against the strong. By that divine strengthening the plundered are enabled to advance successfully against the fortress.