Joseph must have felt betrayed when Mary was discovered to be pregnant. Even so he was willing to protect her by arranging a private divorce (before just two witnesses, cf. Num. 5:11–31). The comment, “a righteous man” (v.19), reminds us that righteousness is not stern insistence on the letter of the law, but is well flavored with mercy and compassion.
Richards, Lawrence O. The Bible Reader’s Companion. electronic ed. Wheaton: Victor Books, 1991. Print.