Isaiah 58:4

Behold, ye fast for strife and debate, and to smite with the fist of wickedness: ye shall not fast as ye do this day, to make your voice to be heard on high.

Behold, you fast for strife and contention, and to strike with the fist of wickedness: you don't fast this day so as to make your voice to be heard on high.

Behold, ye fast for strife and contention, and to smite with the fist of wickedness: ye fast not this day so as to make your voice to be heard on high.

Lo, for strife and debate ye fast, And to smite with the fist of wickedness, Ye fast not as `to'-day, To sound in the high place your voice.

You fast with contention and strife to strike viciously with your fist. You cannot fast as you do today and have your voice be heard on high.