Gregory of Nazianzus

Let us talk about how "mercy is put in the balance" as holy Isaiah declares, for goodness is not without discernment, as the first laborers in the vineyard fancied, because they could not perceive any distinction between those who were paid alike. And [let us talk about] how anger, which is called "the cup in the hand of the Lord" and "the cup of falling which is drained," is in proportion to transgressions, even though he abates to all somewhat of what is their due and dilutes with compassion the unmixed draught of his wrath. For he inclines from severity to indulgence toward those who accept chastisement with fear and who after a slight affliction conceived and are in pain with conversion and bring forth the perfect spirit of salvation. But nevertheless he reserves the dregs, the last drop of his anger, that he may pour it out entire upon those who, instead of being healed by his kindness, grow obdurate, like the hard-hearted Pharaoh, that bitter taskmaster, who is set forth as an example of the power of God over the ungodly.