Adam Clarke Bible Commentary

Ye fast for strife and debate - How often is this the case! A whole nation are called to fast to implore God's blessing on wars carried on for the purposes of wrath and ambition. To smite with the fist of wickedness: ye shall not fast as ye do this day "To smite with the fist the poor. Wherefore fast ye unto me in this manner" - I follow the version of the Septuagint, which gives a much better sense than the present reading of the Hebrew. Instead of רשע לא resha lo, they seem to have read in their copy רש על מה לי rash al mah lli. The four first letters are the same, but otherwise divided in regard to the words; the four last are lost, and א aleph added in their place, in order to make some sort of sense with רשע ל. The version of the Septuagint is, και τυπτετε τυγμαις ταπεινον· ἱνα τι μοι νηστευετε - as above.