There is no punishment for blasphemy in the Quran as Allah and His Messenger are above such things.
Do not insult others as they may insult you AND NO punishment prescribed after saying this.
6:108 (O Believers) Do not insult the idols they set up besides God. They might insult God in their ignorance and hurt themselves. To every community We have made their deeds seem fair. Then to their Lord is their return and He will explain to them exactly what they used to do.
6:109 They swear by God that if a miracle comes to them, they would believe in it (the Book). Say, “All miracles are with God (if you reflect on the Universe). What can make you understand that even if a physical miracle came to them, they would find other excuses and still not believe?
Death sentence is for life for life, those who take life, not apparent blasphemy. Add another human being to the long list of those murdered by the bukharian hadith worshippers, in the name of Allah, Most Merciful, OFT FORGIVING!!!!!!!!!!!!!!!!!!!!. One attribute they will never have.
5:32 On that account, We decreed to the Children of Israel (the Eternal Moral Ordinance for all humanity 2:178) that whoever kills a human being, unless it be for murder or bloody crimes on the earth, it would be as if he killed all mankind. And whoever saves the life of one human being it would be as if he saved the life of all mankind. Our Messengers came to them with evident truth, yet, even after this, many of them continue to commit excesses in the land. [Only a court of law will make decisions. No one would take the law in own hand]
5:33 The just punishment for those who wage war against God and His Messenger and endeavor to commit bloody crimes on earth, is that they be killed or crucified, or have their hands and feet severed on alternate sides, or to be banished from the land. Such is their disgrace in this world, and an awful suffering awaits them in the Hereafter.
[Fasaad = Bloody crimes = Spreading corruption in the land = Creating disorder. ‘God and His Messenger’ … None can physically fight against God, and the Messenger was a mortal man. So, God and the Messenger denote the Central Authority of the Islamic State. Waging war against God and the Messenger would mean rebellion against the Islamic State. ‘Severing the hands and feet’ may also be understood as cutting of their ability to create Fasaad. See 5:38 & 12:31. ‘Banishing from the land’ may indicate exile or imprisonment for life. If they present to the authorities before getting arrested, they could be pardoned. 4:64]