“Cease to do evil, learn to do good; seek justice, correct oppression; bring justice to the fatherless, plead the widow's cause” (v16-17). Isaiah’s role as a prophet was to speak God’s truth into Israel’s current situation (8th century BC). He told the people that God was tired of their “vain offerings” and “solemn assemblies” (v13); their religious rituals were offensive to God because they chased after wealth while ignoring the suffering of the vulnerable (fatherless and widows, v23). Isaiah urged them to repent while there was time.
“Zion shall be redeemed by justice, and those in her who repent, by righteousness” (v27). True repentance means that our hearts are cleansed (v18) and we “learn to do good” (v17).