Isaiah 1:16-20: "Wash yourselves, make yourselves clean;
Put away the evil of your doings from before My eyes. Cease to do evil, 17 Learn to do good; Seek justice, Rebuke the oppressor; Defend the fatherless,
Plead for the widow. 18 Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool. 19 If ye be willing and obedient, ye shall eat the good of the land: 20 But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the LORD hath spoken it."

The Lord GOD invites His people to come reason with Him. What He offers us isn't just offered because He is greater than us and has the right to dictate whatever terms please Him. God's direction for us is reasonable. It is smart. It is the best way to live.
It is madness to reject and resist a God of infinite wisdom, infinite love, infinite grace, and infinite power. True reason will drive any honest man to the humblest adoration and submission towards God. The angels surrounding the throne of God are covered with eyes, which speaks of their great ability to perceive and know (Revelation 4:6-8). These are perhaps the most intelligent, rational beings God ever created, and they spend every moment of their existence lost in total praise, total adoration, and total surrender to God. This is where the highest reason will drive us. It is just plain reasonable to follow God. Have you ever once heard of an old Christian, on their deathbed, gathering their children and friends around, and saying: "Now friends, watch out for that Christianity! I've followed Jesus my whole life and I'm so sorry I did! What a waste that was!" What nonsense! Quite the contrary, we find that Christians on their deathbed are trusting and loving God more than ever. It's just plain reasonable.

In this passage, Isaiah says nothing about how this cleansing comes. But we know that it comes because Jesus took upon Himself our stain of sin, and God judged sin perfectly and completely in Jesus, so we can be accounted white as snow and as white as wool.
There is tremendous hope in God's forgiveness! We really can be clean from the stain of sin. Our good works can't clean the stain. Our best intentions or promises can't clean the stain. Our suffering or pain can't clean the stain. Time can't clean the stain. Death can't clean the stain. Only the work of Jesus can make us white as snow! We really can have a break with the past, and a new beginning in Jesus Christ. The power of sin, the shame of sin, the guilt of sin, the domination of sin, the terror of sin, and the pain of sin can all be taken away in Jesus.

When we consider the greatness of God's cleansing and pardon, it is all the more reason for us to come now. God wants the separation between you and He to be gone now. He doesn't want you to continue in your destructive path another moment. He wants the best for us now.
"Come now, no season can be better. If ye tardy till you're better, ye will never come at all. Come now; you may never have another warning; the heart may never be so tender as it is to-day. Come now; no other eyes may ever weep over you; no other heart may ever agonise for your salvation. Come now, now, now, for tomorrow you may never know in this world. Death may have sealed your fate, and the once filthy may remain filthy still. Come now; for to-morrow thy heart may become harder than stone, and God may give thee up. Come now; it is God's time; to-morrow is the devil's time. 'To-day if ye will hear his voice harden not your hearts, as in the provocation, when your fathers tempted me and proved me in the wilderness and saw my works.' Come now. Why delay to be happy? Would you put off your wedding-day? Will you postpone the hour when you are pardoned and delivered? Come now: the bowels of Jehovah yearn for you. The eye of your father sees you afar off, and he runs to meet you. Come now; the church is praying for you; these are revival times; ministers are more in earnest." (Spurgeon)

Is it willing and obedient or refuse and rebel? No one perfectly matches either phrase, but which phrase better describes your life? There is a consequence for either course: eat of the good of the land or be devoured by the sword. No wonder the LORD said, "Come now, let us reason together!