Numbers 15:35

And the Lord said unto Moses
Who consulted the Lord upon this affair, in the tabernacle, even at the most holy place, from above the mercy seat, where he promised to meet him, and commune with him about whatsoever he should consult him, ( Exodus 25:22 ) ;

the man shall surely be put to death;
for as no fire was to be made throughout their habitations on a sabbath day, gathering sticks for such a purpose was a work that was a violation of the sabbath, punishable with death, ( Exodus 35:2 Exodus 35:3 ) ; and the kind of death follows:

all the congregation shall stone him with stones without the camp;
as afterwards without the city: of the place and manner of stoning, (See Gill on Acts 7:58).