Albert Barnes Commentary 2 Kings 1:10

"And Elijah answered and said to the captain of fifty, If I be a man of God, let fire come down from heaven, and consume thee and thy fifty. And there came down fire from heaven, and consumed him and his fifty." — 2 Kings 1:10 (ASV)

The charge of cruelty against Elijah requires us to consider his motive. His purpose was to make a sharp, public example and to vindicate God's honor in a striking way. Ahaziah had, in effect, challenged Yahweh to a trial of strength by sending a company of fifty men to arrest one person.

Elijah was not Jesus Christ, who was able to reconcile mercy with truth, vindicating God's honor with the utmost tenderness for those who err, and able to awe them merely by His presence . In Elijah, the spirit of the Law was embodied in its full severity. His zeal was fierce; he was not shocked by bloodshed, and he showed no softness or reluctance. He did not fully learn from the warning at Horeb (see the note on 1 Kings 19:12). He continued to be the uncompromising avenger of sin and the wielder of the Lord's terrors, just as he had shown himself at Carmel.

Consequently, he is no pattern for Christians (Luke 9:55), but his character is the perfection of the purely legal type. No true Christian after Pentecost would have done what Elijah did. However, what he did, at the time he did it, was not sinful; it was simply executing strict, stern justice. Elijah asked for fire to fall, and God made it fall. In doing so, God both vindicated His own honor and justified the prayer of His prophet.