Because we live on this side of Christmas, we want to rush to the end of the story where everything turns out okay. We miss the anxiety in a young woman's announcement, "I'm pregnant" and the tension on a man's brow as he parses the right decision. You might even be tempted to think Joseph was slow spiritually and should have figured out what was going on a lot sooner. But if you do that, you miss the whole point of what Joseph is learning, and of what we can learn from him—that there's some amazing stuff going on around Christmas besides how Jesus got here. You miss out on how God is already beginning to redefine what true righteousness is.
Matthew 1:1819 tells us: "This is how the birth of Jesus Christ came about: His mother Mary was pledged to be married to Joseph, but before they came together, she was found to be with child through the Holy Spirit. Because Joseph her husband was a righteous man and did not want to expose her to public disgrace, he had in mind to divorce her quietly."
Joseph, Scripture says, was a righteous man. There's a rich history behind this idea. The Hebrew word for a righteous man is tsaddîyq. Joseph was a tsaddîyq, and this means he was known for his uncompromising obedience to the Torah, the law of Moses. (For some of this concept I'm indebted to an article by Scott McKnight, a New Testament scholar.)
Joseph didn't eat unclean food. He didn't mix with the wrong kinds of people. He didn't keep his carpentry shop open on the Sabbath to make a few extra drachmas. He was a tsaddîyq; that was his identity. Everybody knew this about him. Nobody invited Joseph over to have ham sandwiches with tax collectors and prostitutes. He was what people wanted to be. Like a businessman ...