One Sabbath day, long ago, a man went out to gather sticks. His neighbors saw this, and brought him before the court. The jury found him guilty, and the judge pronounced sentence. Death! Why? Isn't this drastic? How does the debate over the distance of a Sabbath day's journey fit into it?
What was wrong with gathering sticks on the Sabbath? What if it was cold outside and the man needed to keep his fire going? Is gathering sticks such strenuous work?
Christians, who are fairly Torah-ignorant, often assume that the man was gathering the sticks for sale. The Bible doesn't state this. Also, you don't need to add this assumption to the Bible to understand why the death penalty was called for.
Let's look at our source texts before moving on to a discussion of these issues.
Exodus 16:23-39 And he said unto them, This is that which Jehovah hath said, To morrow is the rest of the holy sabbath unto Jehovah: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning. And they laid it up till the morning, as Moses bade: and it did not stink, neither was there any worm therein. And Moses said, Eat that to day; for to day is a sabbath unto Jehovah: to day ye shall not find it in the field. Six days ye shall gather it; but on the seventh day, which is the sabbath, in it there shall be none. And it came to pass, that there went out some of the people on the seventh day for to gather, and they found none. And Jehovah said unto Moses, How long refuse ye to keep my commandments and my laws? See, for that Jehovah hath given you the sabbath, therefore he giveth you on the sixth day the bread of two days; abide ye every man in his place, let no man go out of his place on the seventh day.
Numbers 15:32-36 And while the children of Israel were in the wilderness, they found a man that gathered sticks upon the sabbath day. And they that found him gathering sticks brought him unto Moses and Aaron, and unto all the congregation. And they put him in ward, because it was not declared what should be done to him. And Jehovah said unto Moses, The man shall be surely put to death: all the congregation shall stone him with stones without the camp. And all the congregation brought him without the camp, and stoned him with stones, and he died; as Jehovah commanded Moses.
1 Samuel 15:23 For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry.
Exodus 35:3 Ye shall kindle no fire throughout your habitations upon the sabbath day.
What if the man was cold? He should have gathered enough sticks the previous day. Even if he didn't, he should have gone to his neighbors tent to share their fire if cold was the problem. On the Sabbath, noone should be lonely or destitute of the needs of life.
Kindling a fire was a preparation for work; the work of cooking. When Moses said do not kindle a fire, he wasn't saying to freeze to death. He was saying "do your baking and food preparation the day before". You have heard it said, a woman's work is never done. But I say to you, on the Sabbath, even a woman's work is done.
Here we have one possible explanation of the death penalty. For the man to be out gathering sticks of wood implies he was going to kindle a fire. This implies he was going to do some cooking. But he had been clearly instructed to prepare food the day before. His action was prima facie evidence of intent to rebel. Since the penalty for witchcraft is death, and rebellion is like unto witchcraft, the penalty is also death.
The matter goes deeper. The man gathering sticks was guilty of an actual crime. Moses said that on the Sabbath, you shall not stir out of your place. Anciently, cities and encampments had boundaries called suburbs. The Bible sets these suburbs as 1000 feet from the edge of the camp or city, all around. After this perimiter of 1000 feet in every direction, the fields and factories started. This served to keep cities small. Everyone in the city could walk to their work in the countryside in very short order. Animals would graze in the suburbs, which were open plains where merchants could hold their fairs, and the people of the city could play sports, go for a stroll, and hold religious festivals.
The Pharisees, the Essenes, and Jesus himself had a concept of a "Sabbath Day's Journey". This is a legitimate concept, based on the boundary of the camp or city. If you can't leave your place, you still need to use the washroom. The trees and bushes in the thousand foot perimeter served this function. But to go beyond the perimiter was again, prima facie evidence that you were going out to work. But it was also a direct violation of the command not to go out of your place on the Sabbath.
The man picking up sticks was in direct violation of the "Sabbath Day's Journey" statute, thus directly rebelling. He was stoned to death.
Don't rebel against God.