It is objected that Exodus 31:15 already indicated that anyone working on the sabbath should be put to death, so there was no reason to wonder about what ought to be done with the man in Numbers 15.

On the contrary, Moses had to be called to determine a) whether what the man did constituted "work", and b) the method of execution, as neither was specified in Exodus. Critics often confuse the strict statements of the law with the administration of the law.

From a Christian perspective, the strict laws of the Old Covenant served as severe, pedagogical boundaries for an ancient people. However, even when a law is clear and an offense is obvious, the administration of justice still requires bringing individuals to trial before a judge. The ancients were no different than we are in this regard.