אֲמַרְתֶּ֕ם שָׁ֖וְא עֲבֹ֣ד אֱלֹהִ֑ים וּמַה־בֶּ֗צַע כִּ֤י שָׁמַ֙רְנוּ֙ מִשְׁמַרְתּ֔וֹ וְכִ֤י הָלַ֙כְנוּ֙ קְדֹ֣רַנִּ֔ית מִפְּנֵ֖י יְהוָ֥ה צְבָאֽוֹת׃
Ye have said: ‘It is vain to serve God; and what profit is it that we have kept His charge, and that we have walked mournfully because of the LORD of hosts?
Read halakhic rulings (Jewish law) on Malachi 3:14: and classical halakhic sources.