Albert Barnes Commentary Luke 24:31

"And their eyes were opened, and they knew him; and he vanished out of their sight." — Luke 24:31 (ASV)

Their eyes were opened. The obscurity was removed. They saw him to be the Messiah. Their doubts were gone, and they saw clearly that he had risen and was truly, as they had long hoped, the Saviour of men. It is not meant that they were previously blind, but that they did not know until then who he was.

He vanished out of their sight. He suddenly departed. It does not appear that there was anything miraculous in this, but, during their surprise, he took the opportunity suddenly to withdraw from them.