הלכה אויף קהלת 9:18

It is taught in a beraita: Rabbi Meir said: When I came to Rabbi Ishmael he said to me: My son, what is your occupation? I said to him: I am a scribe. He said to me: My son, be scrupulous with your work for it is heavenly work. Lest you omit one letter or you add one letter it could come out that you destroyed the entire world. (Eiruvin 13:a) From here one sees how a sofer must be in extreme awe of Hashem. If he makes a blemish or if he doesn’t make a correction properly, he causes his soul to be lost. Since he steals from the masses and causes them to sin leaving them without fulfilling a commandment and making blessings in vain. Concerning him scripture states: One sinner destroys much good. And it also states: Cursed is he who does the work of Hashem with deceit. Therefore he who is fitting and have the power should appoint proper sofrim, men of truth, who hate bribes, Torah scholars, who fear G-d and tremble at His words, in every city and in every town just as shochtim are appointed and examined. All who writes good and valid Sifrei Torah, tefillin, and mezuzot according to all his abilities, his reward is doubled and redoubled and he is saved from the judgement of Gehinnom. (From the Laws of Writing Tefillin by Rabbi Avraham of Sinsheim and from the Levush)

A man whose vices exceed his virtues presently dies in his wickedness, even as it is said: "For the multitude of thine iniquity" (Hos. 9. 7). So is a state whose vices exceed presently destroyed, even as it is said: "Because the cry of Sodom and Gomorroh is great (Gen. 18. 20). So, too, is the whole world, if their vices exceeded their virtues they are presently destroyed, even as it is said: "And God saw that the wickedness of man was great" (6. 5). But the weighing of this is not according to the number of virtues and vices, but according to their magnitude. There is a virtue that overbalances many vices, even as it is said: "Because in him there is found some good thing" (I Kings, 14. 13); and there is a kind of vice which overbalances many virtues, even as it is said: "But one sinner destroyeth much good" (Ecc. 9. 18). Moreover these are not weighed by anyone, save only in the knowledge of the All-knowing God, for only He knoweth the estimate of virtues versus vices. (³Yebamot, 50a; Kiddushin 40a. C.)