Colossians 4:14-18

v14: The mention of Demas warns us about the danger of making "a significant profession of faith" and then later rebelling and deserting Christ as he did.

v15-16: Not all the letters that the apostles wrote have been preserved for us in the New Testament, like the letter which Paul wrote to the church in Laodicea.  If a letter of an apostle is now lost, it "did not belong to the canon" of Scripture.  The Bible we have is complete and contains all we need to know about how to be saved by Christ and live a life that pleases Him.  Therefore it is to be read publicly whenever the church gathers.

v17: The ministry God has given us to do, we are to diligently carry out and persevere in, for as long as He wants us to.  There will be occasions when we need to be reminded of our duty and encouraged to fulfil it.

v18: Remembering that Paul was in prison when he wrote this letter, shows his willingness to suffer for its message.  The teaching of Colossians is to be taken seriously by us.