Our mutual friend Watson delivered to me your recent inquiry into mysteries Messianic. As an amateur genealogist, you pointed out that the genealogy of Jesus found in Matthew 1 describes Joseph as a descendant of David. However, you ask if Jesus would be considered a ‘son of David’ since Joseph was not his…biological…father?
Of course, the genealogy is Mathew’s way of validating the Davidic pedigree of Jesus, as popular apocalyptic sentiment in first century Judea was that God's messiah would be a priestly king type who would restore the Davidic throne in Jerusalem (see Isaiah 11). So it's important that if Jesus is the messiah he must be of Davidic heritage (also, it helps to be from David's hometown Bethlehem; as in Micah 5).
But pay attention to trifles! Notice that Matthew is doing something else here. He mentions several women in the lineage (Tamar, Rahab, Ruth, Bathsheba, and Mary the mother of Jesus). Tamar was the widow of Judah's son, who deceives Judah into taking her into his household by disguising herself as a prostitute and conceiving a child with him (Genesis 38). Rahab was a prostitute who led the Israelite spies into Jericho to do recon work (Joshua 2). Ruth was a foreign (Gentile) widow who marries a wealthy Hebrew (Ruth). Bathsheba slept with King David while her husband Uriah fought in a war (jury is out whether she consented); David had her husband put on the front lines to be killed in order to hide the child he conceived with her (2 Samuel 11).
Why would Matthew go to such pains to mention these women of...questionable reputation?
But then the last woman mentioned is Mary, who conceives a child out of wedlock and her betrothed isn't the father. Quite the scandal, one might imagine.
Clearly, what is on everyone's mind in Matthew's community is not just Jesus' Davidic pedigree, but also his status as an illegitimate son (a "mamzer" or bastard). Indeed, some of the earliest anti-Christian propaganda focused on the circumstances of Jesus' illegitimacy; some attacks included accusations that his real father was Roman centurion named "the Panther"!
What legitimizes Jesus in the eyes of his hometown is Joseph's willingness to claim Jesus as his son—to adopt him, circumcise him and name him. In doing this, Joseph bestows upon Jesus his own Davidic pedigree, and quashes any questions about his legitimacy.
Mathew’s genealogy is relevant to this day:
1. In reading the questionable women in Jesus’ genealogy, we are reminded that one does not have to be perfect to be an important, influential, and integral part of God’s kingdom.
2. Reputation is immaterial. That Jesus was accused (and to an extent rightly so) of being a mamzer, only heightens his solidarity with the marginal, outcast, and misfit. Pedigree, distinction and class are irrelevant to the kingdom.
3. Just as Jesus was legitimated in his adoption by Joseph, so are we made legitimate in our adoption as children of God. As the Apostle once wrote, we have received a spirit of adoption and cry Abba, Father! In other words, the father of Jesus is our Father, too.
And there, my dear Jacobson, lies the crux of the matter.
Sincerely Yours,
S.H.