Albert Barnes Commentary 2 Kings 2:12

"And Elisha saw it, and he cried, My father, my father, the chariots of Israel and the horsemen thereof! And he saw him no more: and he took hold of his own clothes, and rent them in two pieces." — 2 Kings 2:12 (ASV)

The chariot of Israel and the horsemen thereof - These difficult words likely refer to Elijah, whom Elisha addresses as “the true defense of Israel, better than either the chariots or horsemen” that he saw. Therefore, he tore his clothes as a sign of his grief.