According to the New Testament, the God of Israel becomes
mortal: Immanuel, God with us.
God can descend as an adult and live as a God.
God can choose birth to a royal house and live as a man of the educated
Instead, God decides to break the Law of Moses by impregnating a young,
unmarried peasant girl who is already betrothed and likely to suffer execution by stoning for the crime of adultery.
“Now the birth of Jesus Christ took place in this way. When his mother Mary had been betrothed to Joseph, before they came together she was found to be with child from the Holy Spirit. And her husband Joseph, being a just man and unwilling to put her to shame, resolved to divorce her quietly.”Matthew 1:18-19
Joseph later adopts Jesus as his own.
Everything about the birth of Jesus is unsavory in terms of Mosaic Law and the rigid class system of the ancient world.
“Unlawful intercourse with a woman betrothed to a man was adultery, because the betrothed woman was deemed as inviolable as the married woman. The punishment for this crime was stoning to death at the place of public execution (Deut. xxii. 24). The punishment for Adultery according to the Mishnah (Sanh. xi. 1) was strangulation; the rabbinical theory being that wherever the death penalty was mentioned in the Bible, without any specific statement of the manner of its infliction, strangulation was meant. The Jewish Encyclopedia
The child of an incestuous or adulterous relationship was branded a mamzer.
A mamzer was not permitted to become a member of the Jewish body politic (Deut. xxiii. 3 [A. V. 2]), and could not intermarry with a Jew or Jewess (Ḳid. iii. 12), although it did not lose its right to inherit from the husband of its mother, who, while not the legitimate father, was for this purpose the putative father.”’ The Jewish Encyclopedia
There is no room at the inn for Mary’s mamzer, so he is born in a cave where he sleeps in a device for feeding livestock.