Is 1 Corinthians 7:26–40 not the 'Word of God'? Paul makes it clear that the following section is not a command from God but his own opinion:


  Now concerning the betrothed, I have no command from the Lord, but I give my judgment as one who by the Lord's mercy is trustworthy. (1  Corinthians 7:25, ESV)


Does this mean that 1 Corinthians 7:26–40 is not the 'Word of God'? If it is, how can this be explained? If it isn't, doesn't this call some other verses, particularly from the epistles, into question, i.e., that they might be just the writer's opinion?
One of the things it is important to realize about the Bible is that the authors did not sit down to 'write the Bible'. Books of the Bible have to be taken first as what they were intended by their authors to be - a biography of Jesus, a history of the early church, or a letter to one of the churches. Yes, God did inspire those authors to write something that would be infallible and of eternal value, but he did not simply dictate a message for all people for all time which Paul or whoever then wrote down. It's highly likely that Paul did not realize that he was writing Infallible Scripture when he did it. He certainly wrote other letters that are not included in Scripture.

Because of this we find things in the Epistles which are of unclear value to those of us who read them 2000 years later. Paul asks the church to greet specific people that he knows. That isn't God instructing us to greet those people, it's Paul sending a greeting to people he knows. It's part of God's awesome power that he can use those writings to instruct us, without making everything a direct commend from him.

In other words, God inspired Paul to write those words in his letter. The fact that they are Paul's opinion (but a divinely inspired opinion) are unimportant. They are meant to be there, and they are just as inspired as every other part of the Epistle. The Bible also contains many other things that are not the direct command of God - stories of people who did less-than-righteous things; opinions offered by characters that do not necessarily reflect God's opinions

Why did God cause Paul to write his own opinion as part of Scripture? A good questions, which I don't have a definitive answer for. Maybe it was to draw attention to the fact that Christianity is not just a set of written rules, but sometimes calls for us to use the Holy Spirit that he gave us to work out what the right thing to do is. But I speculate. The answer here is that there is no conflict between Paul writing something that is his opinion, and the fact that God inspired him to write exactly that.