This longish quote packed with truth is deserving of careful meditation. The commentary is based on 1 Timothy 6:20: “O Timothy, protect what has been entrusted to you. Avoid the profane chatter and absurdities of so-called ‘knowledge'” (NET).
Second, Paul’s language emphasizes continuity. Timothy was to carry on with a mission given by Christ to the apostles much earlier (compare 1 Cor 15:1-3; 2 Tim 2:2). The gospel ministry is a single (though multifaceted) task with a single message, which is to be transmitted through the generations by servants whom God chooses (2 Tim 2:2).
Third, this task is a sacred one, as Paul’s choice of “deposit” terminology confirms. God has planned that the evangelistic mission be executed by the proclamation of the gospel. The mission depends on the gospel message. Consequently, God’s servants in each generation must guard it–that is, faithfully proclaim and protect it. The threat to the message and the church’s mission posed by the false teachers in Ephesus was Paul’s main reason for writing.