Complex sentence: They advocate Keeping God's Laws, including the literal seventh day Sabbath, because obedience to Gods Law is what God expects of those who love Him; disobedience to Gods Law is what defines sin.
Split into simpler sentences: They advocate Keeping God's Laws, including the literal seventh day Sabbath, because obedience to Gods Law is what God expects of those who love Him. Additionally, disobedience to Gods Law is what defines sin.