James and John - They were called Boanerges - sons of thunder - probably on account of their energy and power in preaching the gospel, or of their vehement and rash zeal - a remarkable example of which we have in this instance, Mark 3:17.
Wilt thou ... - The insult had been offered to Jesus, their friend, and they felt it; but their zeal was rash and their spirit bad. Vengeance belongs to God: it was not theirs to attempt it.
Fire from heaven - Lightning, to consume them.
As Elias did - By this they wished to justify their zeal. Perhaps, while they were speaking, they saw Jesus look at them with disapprobation, and to vindicate themselves they referred to the case of Elijah. The case is recorded in 2 Kings 1:10-12.