Prov 17:15
He that justifieth the wicked, and he that condemneth the just, even they both are abomination to the Lord.
Isa 5:23
Which justify the wicked for reward, and take away the righteousness of the righteous from him!
Mic 3:11
The heads thereof judge for reward, and the priests thereof teach for hire, and the prophets thereof divine for money:
Who are these who justify the wicked for reward and condemn the just?
It refers to those under the old covenant works of the law for righteousness. They suppress the truth of the gospel, in unrighteousness. They will not submit to God's righteousness and they try to deceive others into following their path of unrighteousness/being perfected by the flesh. They follow the ministry of condemnation/death, 2Cor 3:7.
Rom 1:18-19
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth (of the gospel) in unrighteousness (rebellion against God seeking to establish their own righteousness), because what may be known of God is manifest in them, for God has shown it to them.