Albert Barnes Commentary 1 Kings 19:15

"And Jehovah said unto him, Go, return on thy way to the wilderness of Damascus: and when thou comest, thou shalt anoint Hazael to be king over Syria;" — 1 Kings 19:15 (ASV)

The answer is not a justification of God's ways, nor a direct rebuke of the prophet's weakness and despair, nor an explanation or application of what Elijah had seen. For now, he is simply directed back to the path of practical duty. His mission is not yet over; there is still work for him to do.

He receives specific instructions regarding Hazael, Jehu, and Elisha. He is comforted with a revelation well-suited to rouse him from his despair: there are seven thousand who will sympathize with him in his trials and who need his care and attention.

The wilderness of Damascus - This was probably the district north of the prophet’s own country, between Bashan and Damascus itself, which was later known as Iturea and Gaulanitis. Here the prophet could be secure from Jezebel, while he could easily communicate with both Israel and Damascus and carry out the commissions with which he was entrusted.

When you come, anoint - Rather, “and you shall go and anoint.” Elijah performed only one of the three commissions given to him. He appears to have been left free to choose the time for carrying out his commissions, and it seems that he thought the proper occasion had not yet arisen for either the first or the second before his own translation. But he took care to communicate the divine commands to his successor, who performed them at the fitting moment (marginal references).