The Shin Bet security service says Khalil Khalil, born in 1990, had joined a gym at the Hebrew University in Jerusalem to physically prepare for the mission.
The agency says he told his family he was going on a religious pilgrimage to Mecca, but instead, he and a friend flew to Istanbul in January and then traveled to a safe house in southern Turkey. From there, smugglers brought them to Syria.
Khalil returned after a few weeks and was later arrested by the Shin Bet.