Albert Barnes Commentary Isaiah 1:16

"Wash you, make you clean; put away the evil of your doings from before mine eyes; cease to do evil;" — Isaiah 1:16 (ASV)

Wash you - This is, of course, to be understood in a moral sense, meaning that they should put away their sins. Sin is represented in the Scriptures as defiling or polluting the soul (Ezekiel 20:31; Ezekiel 23:30; Hosea 5:8; Hosea 9:4).

The removal of sin is represented by the act of washing. For example, David prays, Wash me thoroughly from mine iniquity, and cleanse me from my sin (Psalms 51:2). Jeremiah also exclaims, O Jerusalem, wash thine heart from wickedness, that thou mayest be saved (Jeremiah 4:14). (1 Corinthians 6:11; Hebrews 10:22; 2 Peter 2:22; Revelation 1:5; Revelation 7:14).

This command to wash is used here in close connection with the previous verse, where the prophet says that their hands were filled with blood. He now admonishes them to wash away that blood, with the implied understanding that then their prayers would be heard.

It is also noteworthy that the prophet directs them to do this themselves. He addresses them as moral agents and as having the ability to do it. This is the consistent way God addresses sinners in the Bible, requiring them to put away their sins and to make themselves a new heart .

The evil of your doings - This is a Hebraism, meaning your evil doings.

From before mine eyes - As God is omniscient, to put them away from before his eyes is to put them away altogether. To pardon or forgive sin is often expressed by hiding it (Psalms 51:9): Hide thy face from my sins.

Cease to do evil - (Compare 1 Peter 3:10–11). The prophet is specifying what was necessary so that their prayers might be heard and they might find acceptance with God. What he states here is a universal truth. If sinners wish to find acceptance with God, they must come renouncing all sin, resolving to put away everything that God hates, however dear it may be to the heart .