"Who are you, O man, to answer back to God? Will what is molded say to its molder, 'Why have you made me like this?' Has the potter no right over the clay to make of the same lump one vessel for honorable use and another for dishonorable use?" (Romans 9:20-21).
"Now in a great house, there are not only vessels of gold and silver but also of wood and clay, some for honorable use, some for dishonorable. Therefore, if anyone cleanses himself from what is dishonorable, he will be a vessel for honorable use, set apart as holy, useful to the master of the house, ready for every good work" (II Timothy 2:20-21).
The first text above, Romans 9:20-21, is one of the classic prooftexts for the biblical doctrine of reprobation, the understanding that God has chosen the nonelect to remain in unbelief, and receive the judgment of damnation in Hell. The Apostle did not create this analogy, but rather borrows it from Isaiah 29:16: "You turn things upside down! Shall the potter be regarded as the clay, that the thing made should say of its maker, 'He did not make me': or the thing formed say of Him who formed it, 'He has no understanding.'" And Jeremiah 18:6: "'O house of Israel, can I not do with you as this potter has done?' declares the Lord. 'Behold, like the clay in the potter's hand, so are you in My hand, O house of Israel.'"
People who hold to any level of Pelagianism avoid Romans 9:21, as they do, in fact, the entire chapter. To say that God claims the right of creator to use His creations as His glory requires is to deny any amount of sovereignty in humans. Yet, just as Satan offered Adam and Eve in Genesis 3:5, the semi-Pelagian advocates an autonomy in men, as if we were self-created and self-redeemed.
God knows nothing of such autonomy, but, instead, claims the same sovereignty over His human creations as the potter claims over the clay, to make some into vessels of honor, that is, of holiness and blessedness, and others into vessels of dishonor, that is, into holders of wastes to be shattered and discarded (See Leviticus 6:28, 11:33, etc.).