[Elisha] went up from there to Bethel, and while he was going up on the way, some small boys came out of the city and jeered at him, saying, “Go up, you baldhead! Go up, you baldhead!” And he turned around, and when he saw them, he cursed them in the name of the Lord. And two she-bears came out of the woods and tore forty-two of the boys. (2 Kings 2:23-24 ESV)
While the commentators have given some interesting (and doubtful) interpretations of this verse, the most reasonable and helpful comment I've seen is why the boys used the term "Go up... go up..." It was most likely a reference to Elija, who was Elisha's mentor, who went up into the sky to be with King Jesus, rather than die. Possibly these boys were expressing their desire that he leave the earth and never come back. Might as well wish him dead.
Secondly, it must be noted that it was God, not Elisha, who actually sent the bears. Elisha did not send them.
Finally, the best interpretation of this verse came earlier in the Bible as a solemn warning to the parents of Israel:
Then if you walk contrary to me and will not listen to me, I will continue striking you, sevenfold for your sins. And I will let loose the wild beasts against you, which shall bereave you of your children and destroy your livestock and make you few in number, so that your roads shall be deserted. (Leviticus 26:21-22 ESV)
This Scripture really puts the fear of God in me. DO NOT MOCK GOD OR GOD'S ANOINTED. The fear of the Lord is the beginning of wisdom (Proverbs 1:7).
Remember, O Lord, how your servants are mocked,
and how I bear in my heart the insults of all the many nations,
with which your enemies mock, O Lord,
with which they mock the footsteps of your anointed. (Psalm 89:50-51 ESV)
It is a fearful thing to fall into the hands of the living God. (Hebrews 10:31 ESV)