"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 the Lord 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 the Lord commanded Moses."
That's a little bit of a tough pill to swallow. Why exactly did this man deserve death because he decided to gather stones on the Sabbath? After all, it seems like such a small infraction of the law, so why the harsh punishment?
Perhaps, verses 30-31 provides us our best answer.
"But the soul that doeth ought presumptuously, whether he be born in the land, or a stranger, the same reproacheth the Lord; and that soul shall be cut off from among his people. Because he hath despised the word of the Lord, and hath broken his commandment, that soul shall utterly be cut off; his iniquity shall be upon him."
Because he hath despised the word of the Lord and hath broken His commandment.... It would seem that the real reason that this man was stoned wasn't for picking up sticks but because his attitude was troublesome.
He treated the word of the Lord as if it didn't matter, and thus had no difficulty breaking that commandment. If we're truly honest with ourselves, we would note that the idea that this (or any other sin) is just a small infraction of the commands of God is indicative of the same attitude. Apparently, some things the Lord says don't matter as much as other things that we see have a clearer effect upon the world at large.
So here's a reminder for you - there are no such things as little sins. They are all pretty monstrous.