John Gill Commentary Habakkuk 1:2

"O Jehovah, how long shall I cry, and thou wilt not hear? I cry out unto thee of violence, and thou wilt not save." — Habakkuk 1:2 (ASV)

O Lord, how long shall I cry, and you will not hear !
&c.] The prophet, having long observed the sins and iniquities of the people among whom he lived, and being greatly distressed in his mind on account of them, had frequently and importunately cried to the Lord to put a stop to their abounding, that the people might be brought to a sense of their sins and reform from them. But nothing of this kind appearing, he concludes his prayers were not heard, and therefore expostulates with the Lord upon this head.

[even] cry to you [of] violence, and you will not save !
This refers either to violence done to himself in the discharge of his office, or violence of one man to another, from the rich to the poor. And yet, though he cried again and again to the Lord to check this growing evil and deliver the oppressed out of the hands of their oppressors, it was not done, which was a matter of grief and trouble to him.