On the night of Friday, October 6, Jon Polin and Rachel Goldberg laid their hands on the head of their 23-year-old son, Hersh, so that they could bless him, a ritual of the Sabbath. They recited in Hebrew: May you feel God’s presence within you always, and may you find peace. It was an exquisitely temperate Jerusalem evening, and the Goldberg-Polin family made the most of it, dining al fresco at a long table of friends. Hersh’s presence was an unexpected blessing. He had only recently returned from several months of traveling across Europe by himself, occasionally meeting up with his boyhood friends. Earlier in the week, Hersch had told his mother that he would be away for the weekend, attending a music festival in the north. But that festival’s organizers had neglected to obtain the necessary permits, and the event ended prematurely. As Rachel stared at her son from across the table, she marveled at his hard-earned sense of ease. When the Goldberg-Polin family emigrated from Richmond, Virginia, in 2008, when Hersh was 7, …