Luke 13:4

Now one tower is compared to the whole city, that the destruction of a part may alarm the whole. Hence it is added, But, except ye repent, ye shall all likewise perish; as if He said, The whole city shall shortly be smitten if the inhabitants continue in impenitence.

(ubi sup.) Again, there had been eighteen others crushed to death by the falling of a tower, of whom He adds the same things, as it follows, Or those eighteen upon whom the tower of Siloam fell and slew them, think ye that they were sinners above all men that dwell in Jerusalem? I tell you, Nay, For he does not punish all in this life, giving them a time meet for repentance. Nor however does he reserve all for future punishment, lest men should deny His providence.

Those men of Jerusalem also who were crushed by the falling of the tower, signify that the Jews who refuse to repent will perish within their own walls. Nor without meaning is the number eighteen given, (which number among the Greeks is made up of Ι and Η, that is, of the same letters with which the name of Jesus begins.) And it signifies that the Jews were chiefly to perish, because they would not receive the name of the Saviour. That tower represents Him who is the tower of strength. And this is rightly in Siloam, which is interpreted, "sent;" for it signifies Him who, sent by the Father, came into the world, and who shall grind to powder all on whom He falls.

(de Laz. Conc. 3.) For God punishes some sinners by cutting off their iniquities, and appointing to them hereafter a lighter punishment, or perhaps even entirely releasing them, and correcting those who are living in wickedness by their punishment. Again, he does not punish others, that if they take heed to themselves by repentance they may escape both the present penalty and future punishment, but if they continue in their sins, suffer still greater torment.