Matthew 1

"This is how the birth of Jesus the Messiah came about: His mother Mary was pledged to be married to Joseph, but before they came together, she was found to be pregnant through the Holy Spirit. Because Joseph her husband was faithful to the law, and yet did not want to expose her to public disgrace, he had in mind to divorce her quietly."

There is time in life that we might want to make a judgment on someone and we might even want to expose someone's wrongdoing to public disgrace. Although it maybe lawful to do such thing, here Joseph did not do it and instead he wanted to settle it quietly (Joseph didn't know that Mary was pregnant through the Holy Spirit), and the key reason here was that Joseph "did not want to do it", and I think because Joseph loved Mary and want to save her some trouble (stone to death), and Joseph thought the best bet for him to keep faithful to the law is to divorce her quietly.

Joseph has made a decision based on the love of God first (keep faithful to the law by divorcing Mary), and the love of Mary (divorcing her quietly instead of exposing her).

We have to ask ourselves what is the motive behind our action. Is it based on love (to God and others) or for our self righteousness? If it is for our self righteousness, then remember that there is no one righteous, and the righteous will only live by faith in Christ Jesus.