Paul's Opinion and Inspiration

The texts in question are:

1 Corinthians 7:12 To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her.

1 Corinthians 7:40 In my judgment, she is happier if she stays as she is and I think that I too have the Spirit of God.

In 1 Corinthians 7:12, Paul is addressing the fact that Christ did not directly say anything about the issue at Corinth when he spoke about divorce and marriage (Matt. 5:31-32; 19:4-12). However, Paul gives his authoritative view on whether a believing wife should stay with an unbelieving husband. But note, Paul's comments are bracketed by these verses:

1 Corinthians 2:13 This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, explaining spiritual realities with Spirit-taught words.

and

1 Corinthians 14:37 If anyone thinks they are a prophet or otherwise gifted by the Spirit, let them acknowledge that what I am writing to you is the Lord's command.

Paul was clearly speaking by divine authority (1 Cor. 7:40 - "I think that I too have the Spirit of God").

Please see:

Why should I listen to Solomon?
God's Flawless Word
Inspiration and Accuracy
Inerrancy and Canonicity