David Guzik gives an audio teaching on 1 Samuel 23:1-13! David saves the city of Keliah from the Philistines. Here is a link to David Guzik's commentary on 1 Samuel 23: enduringword.c...
Perhaps since the outcasts of Israel came to David to Adullam, now was the time and God's calling to call them to defend Keilah just as Saul had defended Jabesh-Gilead from the Ammonites in 1Samuel 11. Perhaps the Urim and Thumim was the reason that Jesus' promise to the overcomers in Pergamos was to give them a white stone, meaning yes to the entrance to the kingdom of heaven.