The chief of Lebanon’s Iranian-backed Hezbollah movement, Hassan Nasrallah, vowed retaliation once again on Friday for the killing of Hamas leader Saleh al-Arouri in an alleged Israeli strike earlier in the week in Beirut. “The murder of al-Arouri … will certainly not go without reaction and punishment,” Nasrallah said during a speech via video link to commemorate the passing away of a Hezbollah official. “If we remain silent about the killing of al-Arouri, Lebanon will be exposed …,” he said, adding that “the response will inevitably come.” The killing of al-Arouri on Tuesday in Beirut’s …