John Calvin on John 1:16 (“And from [Christ’s] fullness we have all received, grace upon grace.”):
[John] declares briefly that we should not seek any blessing at all outside Christ. But this sentence is composed of several clauses. First, he shows that we are all utterly destitute and empty of spiritual blessings. Christ’s riches are intended to help our failure, support our poverty, and satisfy our hunger and thirst. Secondly, he warns us that as soon as we forsake Christ we seek in vain a single drop of happiness, since God has willed that whatever is good will live in him alone. Therefore, we shall find angels and men arid, heaven empty, the earth barren, and all things worthless if we want to share God’s gifts other than through Christ. Thirdly, he reminds us that we do not need to fear that we will lack anything if only we draw from the fullness of Christ, which is in every way so perfect that we will find it to be an inexhaustible fountain indeed (John Calvin, John, The Crossway Classic Commentaries).