Isaiah 1:1 - Isaiah 13:22
Isaiah is expressing in very descriptive words how God is feeling towards Israel and their fake worship with him. They play in sin and then come to his house for worship acting like everything is fine. They left their hands in prayer and he does not hear them. Their sacrifices are pointless.
"To what purpose is the multitude of your sacrifices unto me? saith the Lord: I am full of the burnt offerings of rams, and the fat of fed beasts; and I delight not in the blood of bullocks, or of lambs, or of he goats.
When ye come to appear before me, who hath required this at your hand, to tread my courts?" Isaiah 1:11-12
God wants our hearts. He wants us to want to be with him and live for him all week long. To desire his dreams for our lives. We can play around with our Christianity but we are only fooling ourselves. God knows our sincerity when we come before him at home or when we go to church.