Whereas in the case of the Sabbath breaker Moses had been certain that the sin was punishable by death, and had been certain that the sin was punishable by death, and had been in doubt only concerning the manner of execution, in the case of the blasphemer matters were different. Here Moses was in doubt concerning the nature of the crime, for he was not even sure if it was at all a capital offence. Hence he did not have these two men imprisoned together, because one of them was clearly a criminal, whereas the status of the other was undetermined. But God instructed Moses that the blasphemer was also to be stoned to death, and that this was to be the punishment for blasphemers in the future.
Moses Uncertain How to Execute the Sabbath Violator
Legends of the Jews 4:49