Under the Old Covenant there were many purification laws prohibiting the touching of certain things considered unclean, e.g., the sick, women, the dead (Num. 5; 9.14; Lev. 15.19-24). But under the New Covenant Jesus was operating under in the Gospels, he could touch and heal the sick (including women) and even raise the dead (Mar. 5.39-41; 14:3; Luke 8.43-48).
This last example leads into one of the strongest arguments for showing how the Law of Moses was rendered ineffective not only at the cross, the death of Jesus, but by the teachings and practice of Jesus before the cross.
Hebrews 7.12 says when the priesthood is changed, the Law must by necessity also be changed as well. And according to the previous verse this happened when Christ made his public appearance (paraginomai, Heb 9:11) when God appointed him High Priest! Cp. Heb. 7:15
This is yet another fulfillment of OT prophecies like the all-important Ps 110 where the LXX renders v.3 as the begetting (i.e., procreation) of the human Son of God from the womb. Hence, God makes the following promise about His uniquely procreated human Son:
“You are a priest forever in the order of Melchizedek.” Cp. Heb 7:17
The point is just as Jesus was already the human Messiah, Son of God from the womb (Luke 1.30-35), he was also already High Priest from the womb.
The Hebrews writer goes on to explain how the New Covenant was established by Christ when he arrived, came on the public scene, (paraginomai Heb 9.11).
As a result, the covenant Jesus made before the cross (Mat 26.28; Luke 22.20) was eventually ratified by his death on the cross.
“For where there is a covenant, there must of necessity be the death of the one who made it.” Hebrews 9:16, NASB.