A.T. Robertson Commentary Luke 2:23

"(as it is written in the law of the Lord, Every male that openeth the womb shall be called holy to the Lord)," — Luke 2:23 (ASV)

In the law of the Lord (εν νομω Κυριου). No articles, but definite by preposition and genitive. Vincent notes that "law" occurs in this chapter five times. Paul (Galatians 4:4) will urge that Jesus "was made under the law" as Luke here explains. The law did not require that the child be brought to Jerusalem. The purification concerned the mother, the presentation the son.