12 He at present spares, He will then judge. But when will He judge? When night shall have passed away. For this reason He has said: “In the morning.” When the day shall at last have arrived, night having passed by. Why does He spare them until the dawn? Because it was night. What means, it was night? Because it was the season for mercy: He was merciful, while the hearts of men were hidden. You see some one living ill; you endure him: for you know not of what sort he will prove to be; since it is night; whether he who today lives ill, tomorrow may live well; and whether he who today lives well, tomorrow may be wicked.
For it is night, and God endures all men, since He is of long-suffering: He endures them, that sinners may be converted unto Him. But they who shall not have reformed themselves in that season of mercy, shall be slain. And wherefore? That they may be scattered abroad from the city of the Lord, from the fellowship of Jerusalem, from the fellowship of the Saints, from the fellowship of the Church. But when shall they be slain? “At dawn.” What means, “at dawn”? When night shall have passed away.
Wherefore now does he spare? Because it is the season of mercy. Why does He not always spare? Because, “Mercy and judgment will I sing unto You, O Lord.” Brethren, let no man flatter himself: all the doers of iniquity shall be slain; Christ shall slay them at the dawn, and shall destroy them from His city. But now while it is the time of mercy, let them hear Him. Everywhere He cries out by the Law, by the Prophets, by the Psalms, by the Epistles, by the Gospels: see that He is not silent; that He spares; that He grants mercy; but beware, for the judgment will come.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)