What does Isaiah 1:15 mean?
The people of Israel are engaged in sinful, rebellious lifestyles against God while at the same time bringing their sacrifices and offerings to Him. God has said their offerings are meaningless (Isaiah 1:13) and that His soul hates their religious observations (Isaiah 1:14) because of the Insincerity of their hearts and in their lives.Now the Lord adds that He won't listen to their prayers. He does not want to see or hear any of their communication if their hearts are far from Him. He will close His eyes.
The Lord adds that the hands they are stretching out in prayer are full of blood. Perhaps, this is due to the injustice and oppression of the poor in Israel. Or it may be a reference to the blood of the animal sacrifices offered for the sins of the people. If those sacrifices are made with no sincerity of the heart, the blood that stains their hands is worthless to atone for their sins.