When Isaiah preached his message, who is responsible for the hardened hearts of Israel? (Isaiah 6:9-10)
They were (Acts 28:25-27)
God was (Mark 4:10-12, Luke 8:9-10)
Both were (Matthew 13:10-15, John 12:37-41)

*The Lord Jesus Christ Himself is the Hardening One of Israel, but we are fully responsible for seeing the glory of Christ and believing the gospel message (Isaiah 53:1-12)