Isaiah 58:6 uses the word "fast" figuratively, using the senses of "self denial", "avoidance" or "cessation" that are in the semantic field of of the word (צום). The verse is addressed to the leadership of the society and to the wealthy at a particular time in history, regarding a particular practice, servitude.
The verse starts with a rhetorical question, "Isn't this the fast (self-denial, cessation of) that I would choose?" (הֲלוֹא זֶה, צוֹם אֶבְחָרֵהוּ), and continues with a list of four distinct imperatives:
- Free (open) the bonds of wickedness (פַּתֵּחַ חַרְצֻבּוֹת רֶשַׁע)
- Undo the ties of the yoke [of servitude] (הַתֵּר אֲגֻדּוֹת מוֹטָה)
- Set (send) the downtrodden free (וְשַׁלַּח רְצוּצִים חָפְשִׁים)
- And break every yoke (וְכָל-מוֹטָה תְּנַתֵּקוּ)
The actions are likely representative of four legal aspects of servitude, possibly
- Immediate freeing of indentured servants
- Canceling the legal contracts of servitude
- Rehabilitation of those downtrodden by servitude so that they can be free
- Abolishment of the institution of servitude
The actions are progressive, starting from the immediate but reversible and concluding with the irreversible breaking of the institution of servitude.
The word yoke, referring here to servitude, is used twice, for clarity and undeniability. It might have been a euphemism in the vernacular of the time. Use of a synonym in the second instance could open the door for interpretation and provide wiggle room, which is the opposite of what the prophet intends.