UPDATE 8:09 AM: It appears that based on a new statement from Jamā’at Tawḥīd wal-Jihād they were actually not involved with the kidnapping or production of the below video. As such, the perpetrators are still unknown if one believes Jamā’at Tawḥīd wal-Jihād.
NOTE: The kidnapping and below video’s purpose is to get HAMAS to release all of Jamā’at Tawḥīd wal-Jihād’s members that are in prison. Most importantly, they hope to gain the release of their amīr, Abū al-Walid al-Maqdisī. They already wrote a statement about this on March 6, which you can read here.