John Calvin Commentary Isaiah 40:15

"Behold, the nations are as a drop of a bucket, and are accounted as the small dust of the balance: Behold, he taketh up the isles as a very little thing." — Isaiah 40:15 (ASV)

Behold, the nations are as a drop of a bucket. If we wish to understand the Prophet’s meaning and to read these words profitably, we must (as I remarked a little earlier) understand his purpose. He does not celebrate the greatness of God in a detached manner but extols it with the greatest possible relevance to the present subject. This is so that the Israelites may know that this shield alone is sufficient to protect them and that they will have no reason to fear the efforts, rage, or violence of the world if God is reconciled to them. In this way, they may learn to turn to God’s protection. For if they were not fully convinced of this, various causes of despair would arise at every moment.

Isaiah continues this theme when he says that all nations and peoples are nothing when compared with God; for, by simply breathing on them, he will scatter all the inhabitants of the earth like small dust. Because we are excessively prone and foolishly inventive in creating reasons for distrust, we imagine that everything Satan does to hinder our salvation obstructs God's path.

To correct this error, the Prophet declares that all creatures are nothing before God and that all the nations resemble small and insignificant drops of water. Therefore, we conclude that nothing can be more contrary to reason than to exalt creatures in order to diminish the power of God, which is high above all and should be acknowledged as such.