We'll put aside the debate as to whether zera is physical or figurative for this time. In the mean time, let's assume that zera is speaking of physical descendants, but the question is, does the seed in Isaiah 53:10 belong to the Messiah? or is it a different people it belongs to.
Firstly, Nakdimon, goes out of his way to show that Zera can be used metaphorically, but that's not what I am speaking of in the article: this is what he says:
"Charge #8: Seed/ זָרַע (Zera) (30:15)
עַל-מִי תִּתְעַנָּגוּ עַל-מִי תַּרְחִיבוּ פֶה תַּאֲרִיכוּ לָשׁוֹן | הֲלוֹא-אַתֶּם יִלְדֵי-פֶשַׁע זֶרַע שָׁקֶר
Against whom do ye sport yourselves? Against whom make ye a wide mouth, and draw out the tongue? Are ye not children of transgression, a seed of falsehood,
A seed shall serve him; it shall be told of the Lord unto the next generation.
He will see seed
"20 Thou shalt not be joined with them in burial, because thou hast destroyed thy land, thou hast slain thy people; the seed of evil-doers shall not be named for ever."(Isaiah 14)
"3 But draw near hither, ye sons of the sorceress, the seed of the adulterer and the harlot." (Isaiah 57)
Unless one is going to argue that all the parents of the ones being addressed here are truly considered harlots and evildoers, you are going to have to concede that it's implied here to refer to people who follow the evil works and the ways of adultery like the generations before them, regardless if they are their physical children or not. For all we know most of the parents of those being addressed here have been righteous while they wandered off. This clearly refers to the works of their predecessors rather than their origins. So this charge remains without teeth, is made up from thin air and rabbi Singer is caught lying yet again!"
The one point I want to drive home is not that Zera is metaphorical, I'll grant for arguments sake it's physical, because Nakdimon has made the excellent point that the seed that is seen is not the Messiah's seed.
I postulate that the seed of Isaiah 53:10 is not the Messiah's seed, but it is the seed of Israel whom the Messiah died for. This is the theory that I am putting forward.
Also, Read Psalm 22:
""Psalm 22:27 All the ends of the earth
will remember and turn to the Lord,
and all the families of the nations
will bow down before him,
28 for dominion belongs to the Lord
and he rules over the nations.
29 All the rich of the earth will feast and worship;
all who go down to the dust will kneel before him—
those who cannot keep themselves alive.
30 Posterity will serve him;
future generations will be told about the Lord.
31 They will proclaim his righteousness,
declaring to a people yet unborn:
He has done it!""
We know contextually this is not the seed of God in a physical sense, so who is it referring to? The seed of the Gentiles who come to faith and love the God of Israel as a result of the Messiah. Remember, in my previous articles I have often mentioned that Psalm 22 is Messianic in nature.
In Isaiah 53, we have Jesus the Messiah seeing seed, but not his own seed, but the seed of Israel.
As for seed being spiritual, I direct you to this article right here http://answering-judaism.blogspot.co.uk/2013/11/response-to-uri-yosef-on-isaiah-53-3.html
Hope that this article helps.