Since God's calling is totally unilateral, and since no one can resist His will, why does He find fault in people?
His answer is that God can do whatever He pleases with His creation (verses 20-26). He is the Potter, and the clay cannot legitimately question the Potter's methods or purposes (see Isaiah 29:16; Jeremiah 18:1-11). He, as sovereign ruler over His creation, is under no obligation to tell us why he chooses as he does.
The warp-woof metaphor of Leviticus 13:47-59, the law dealing with leprosy in cloth, reinforces Paul's conclusion. A priest is to examine a cloth thought to be leprous, but make no decision about the disposition of the garment for seven days, during which time it is to remain isolated, separated from the people of Israel (verse 50). After the seven days, He reexamines the suspect garment (verse 51). If the leprosy has spread, "whether warp or woof, . . . it shall be burned in the fire" (verse 52). If the leprosy has not spread yet is still present, the garment is to be washed and isolated for yet another seven days (verses 53-54). If the leprosy has not changed its color after this second week, the garment is to be burned, even though the plague has not spread (verse 55). If the plague has disappeared, then the garment is clean and fit for use after it has been washed a second time (verse 58).
What an example of God's mercy, patience, and long-suffering! He extends mercy on mercy—to a piece of cloth! How much more grace does God show us, the warp and woof of His garment! How much more has He given the Gentiles in offering them spiritual salvation now! How much more will he exhibit when He calls whole nations of Gentiles—when the time is right!
The Mixed Multitude