This one comes from alert reader Cathy who found it in The Magic of Conflict by Thomas Crum:
A long time ago, there was a Christian monastery in Egypt which possessed only one thing of any material value: a set of three beautiful, ancient scrolls on which was written the Holy Scriptures. One day, a monk yelled out to the Abbot that some-one was stealing the scrolls. Sure enough, the Abbot found that two of the scrolls were missing: the thief had dropped the third in his haste to escape. The Abbot grabbed the third scroll and went racing off after the thief. After a long chase, the exhausted thief fell at the Abbot’s feet, expecting some terrible punishment to be inflicted on him. Instead, the Abbot said gently, “My son, you left this scroll behind. The teaching is incomplete without it.” A short time after that, the thief returned to the monastery with the scrolls, and begged to be allowed to stay on as a monk.