Join the Lord's Army

Jack was in front of me coming out of church one day, and the preacher was standing at the door as he always is to shake hands. The preacher grabbed Jack by the hand and pulled him aside.

The Pastor said to him, 'You need to join the Army of the Lord!'
Jack replied, 'I'm already in the Army of the Lord, Pastor.'
Pastor questioned, 'How come I don't see you except at Christmas and Easter?'
He whispered back, 'I'm in the secret service.'