Let us reason together

Come now, and let us have an argument together, says the Lord: how may your sins which are red like blood be white as snow? how may their dark purple seem like wool?
Isaiah 1:18 BBE

Isa 1:19 If you will give ear to my word and do it, the good things of the land will be yours;
Isa 1:20 But if your hearts are turned against me, I will send destruction on you by the sword; so the Lord has said.