וְקָרַבְתִּ֣י אֲלֵיכֶם֮ לַמִּשְׁפָּט֒ וְהָיִ֣יתִי ׀ עֵ֣ד מְמַהֵ֗ר בַּֽמְכַשְּׁפִים֙ וּבַמְנָ֣אֲפִ֔ים וּבַנִּשְׁבָּעִ֖ים לַשָּׁ֑קֶר וּבְעֹשְׁקֵ֣י שְׂכַר־שָׂ֠כִיר אַלְמָנָ֨ה וְיָת֤וֹם וּמַטֵּי־גֵר֙ וְלֹ֣א יְרֵא֔וּנִי אָמַ֖ר יְהוָ֥ה צְבָאֽוֹת׃
And I will come near to you to judgment; and I will be a swift witness against the sorcerers, and against the adulterers, and against false swearers; and against those that oppress the hireling in his wages, The widow, and the fatherless, and that turn aside the stranger from his right, and fear not Me, Saith the LORD of hosts.
Mesilat Yesharim
In the chapter "All are Liable" (Chagiga 5a): "When Rabbi Yochanan would come to this verse, he would weep - 'I will come near you to judgment and I will be a swift witness...' (Malachi 3:5) - a servant whose minor offenses are weighed just like major offenses, is there any remedy for him?
Mesilat Yesharim
Besides all this, all the free time he has left from his affairs, if he is wise, certainly he should not waste it. But rather to immediately grasp hold of it and not be lax in it, utilizing it to toil in the affairs of his soul and the improvement of his service of G-d.
Mesilat Yesharim
Why is this so? Because just like the essence of "watchfulness" involves putting matters to mind, so the essence of laughter is to remove from one's mind straight, rational thinking so that thoughts of fearing G-d do not enter his heart at all.