In his exegesis of Genesis 2:7, Huldrych Zwingli (1484-1531) demonstrates that for the reformers, there are few details in the Scriptures that cannot be drawn out for homiletical and devotional effect. Thus, to Zwingli, the God’s use of clay is not incidental, but rather, this particular material demonstrates the impurity and basic equality of all humanity and the power of God, who shaped us and gave us value.
Then the Lord God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.
Commentary on Genesis 2:7
A lovely metaphor drawn from potters, who mentally conceive the form of some kind of vessel and then, applying their hands to the clay on the wheel, shape the model and finish it. In the same way, whatever God conceives of in his mind instantly takes place if he should will it. . . . The Hebrew signifies both clay and dust, but clay fits better here. These things remind us of our fashioning and origination. First, so that we might learn how impure, how unclean, nay, how humans are nothing without the spirit of God. Truly, clay soils, contaminates and befouls all things. So also the flesh, if left to itself, thinks and does nothing except what is filthy. Then we learn from this passage how unseemly it is for anyone to prefer himself to another, to grow prideful and puff up his chest, because we have all been fashioned from the same clay. What reason can clay and ashes have for haughtiness?
Genesis 1-11, ed. John L. Thompson, Reformation Commentary on Scripture, OT vol. 1, p. 143-44.