The Lord spoke to Ahaz and said, ‘Ask the Lord your God for a sign for yourself coming either from the depths of Sheol or from the heights above.’ ‘No,’ Ahaz answered ‘I will not put the Lord to the test.’

Then Isaiah said:

‘Listen now, House of David:
are you not satisfied with trying the patience of men
without trying the patience of my God, too?
The Lord himself, therefore,
will give you a sign.
It is this: the maiden is with child
and will soon give birth to a son
whom she will call Immanuel,
a name which means “God-is-with-us.”’

Here I am, Lord! I come to do your will.

You do not ask for sacrifice and offerings,
  but an open ear.
You do not ask for holocaust and victim.
  Instead, here am I.

Here I am, Lord! I come to do your will.

In the scroll of the book it stands written
  that I should do your will.
My God, I delight in your law
  in the depth of my heart.

Here I am, Lord! I come to do your will.

Your justice I have proclaimed
  in the great assembly.
My lips I have not sealed;
  you know it, O Lord.

Here I am, Lord! I come to do your will.

I have not hidden your justice in my heart
  but declared your faithful help.
I have not hidden your love and your truth
  from the great assembly.

Here I am, Lord! I come to do your will.

Bulls’ blood and goats’ blood are useless for taking away sins, and this is what Christ said, on coming into the world:

You who wanted no sacrifice or oblation,
prepared a body for me.
You took no pleasure in holocausts or sacrifices for sin;
then I said,
just as I was commanded in the scroll of the book,
‘God, here I am! I am coming to obey your will.’

Notice that he says first: You did not want what the Law lays down as the things to be offered, that is: the sacrifices, the oblations, the holocausts and the sacrifices for sin, and you took no pleasure in them; and then he says: Here I am! I am coming to obey your will. He is abolishing the first sort to replace it with the second. And this will was for us to be made holy by the offering of his body made once and for all by Jesus Christ.

Praise to you, O Christ, king of eternal glory!
The Word became flesh,
he lived among us,
and we saw his glory.
Praise to you, O Christ, king of eternal glory!