I will begin my support of OSAS with Hebrews. This chapter compares the Aaronic and Levitical priesthoods of the Old Covenant with the Melchezedek priesthood of the New Covenant (ie. Christ)
Hebrews 7:11 - 28
A Superior Priesthood
11 Now if perfection could have been attained through the
Levitical priesthood (upon which basis the people received
the Law), why was there still a need for another priest to appear—one in the order of Melchizedek and not in the order of Aaron?
12 For
when the priesthood is changed,
the Law must be changed as well.
13 He of whom these things are said belonged to a different tribe, from which no one has ever served at the altar.
14For it is clear that our Lord descended from Judah, a tribe as to which Moses said nothing about priests.
15 And this point is even more clear if another priest like Melchizedek appears,
16 one who has become a priest not by a law of succession,
but by the power of an indestructible life.
17 For it is testified:
“You are a priest forever
in the order of Melchizedek.”
18 So
the former commandment is set aside because it was weak and useless 19 (
for the Law made nothing perfect), and a
better hope is introduced, by which we draw near to God.
20 And none of this happened without an oath. For others became priests without an oath,
21 but Jesus became a priest with an oath by the One who said to Him:
“The Lord has sworn and will not change His mind,
‘You are a priest forever.’”
22 Because of this oath,
Jesus has become the guarantee of a better covenant.
23 Now there have been many other priests, since death prevented them from continuing in office.
24 But
because Jesus lives forever,
He has a permanent priesthood.
25 Therefore
He is able to save completely those who draw near to God through Him, since
He always lives to intercede for them.
26 Such a high priest truly befits us—One who is holy, innocent, undefiled, set apart from sinners, and exalted above the heavens.
27 Unlike the other high priests, He does not need to offer daily sacrifices, first for His own sins and then for the sins of the people; He sacrificed for sin once for all when He offered up Himself.
28 For the Law appoints as high priests men who are weak; but the oath, which came after the Law, appointed the Son, who has been made perfect forever.
So we can see who and what we now have in Jesus Christ, our Savior as our High Priest and the guarantee'or of the New Covenant which is sealed in God Himself, the Holy Spirit. Notice in verse 12 that the law must change as well. New High Priest, New Covenant, new seal, new law.
Now my second point is that we officially change ownership when we are saved in the New Covenant.
1 Corinthians 7:23
You were bought at a price; do not become slaves of men.
1 Peter 1:18
For you know that it was not with perishable things such as silver or gold that you were redeemed from the empty way of life you inherited from your forefathers,
Revelation 5:9
And they sang a new song: "Worthy are You to take the scroll and open its seals, because You were slain, and by Your blood You purchased for God those from every tribe and tongue and people and nation.
We have been purchased by Jesus for a price. And we have changed masters, from serving self/flesh to serving God. We have not been purchased with silver or gold, which can perish, but with the blood of God Himself who will never perish.
Matthew 6:24
24 No one can serve two masters: Either he will hate the one and love the other, or he will be devoted to the one and despise the other.
