Custodians are people who are to take the responsibility for taking care of something valuable such as paintings, books, even houses. The Jews were proud that they were custodians of the oracles of God. (Romans 3:1-2) But they did not do with the Word what they should have. (Romans 2:17-24)
http://www.granbychurchofchrist.org/Sermons/pages/2014/custodians-of-the-truth.htm
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