Prove my statement wrong.
Did, or did not, Jesus keep the Law? Yes. Was Jesus impure? No. Therefore keeping the Law does not necessitate impurity.
-A8
"Did, or did not, Jesus keep the Law? Yes. Was Jesus impure? No. Therefore keeping the Law does not necessitate impurity."
What's your point? It is agreed that Jesus did not commit sin therefore His baptism was an identification and a sign. It was a voluntary obedience.
Mary's purification rite was different. She had a male son and the law said if a woman has a male son she has to undergo the purification rite to be part of the religious community i.e attend the sanctuary. It was not voluntary. She obeyed because her actions brought her within the Law.
There was no law. John Baptized with water for repentance and preached that those Baptized should produce fruit in the spirit of repentance. Jesus did it to fulfill all righteousness. John had already said that the one who would come would Baptize with the Holy Spirit. Jesus established "the law" when He was Baptized.
Notice the testimony of the Father at that point. The Holy Spirit recognized Himself. Jesus' decision to be Baptized by John shows that Baptism does not imply one has sinned at all, nor does producing fruit in the spirit of repentance. From that point, Baptism was established.