One of the basic precepts of Christianity, as well as Judaism, is that there is an eternal portion of the human being which is eternal, and known as the soul. That precept is loosely based on the idea that man was created in God's image. Looking at Genesis, we find;
Genesis 1:27 KJV So God created man in his own image, in the image of God created he him; male and female created he them.
Genesis 2:7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.
So the breath of life is the creator of the soul in both religions. That coming from God which is eternal would also be eternal, and the product of that would also be eternal.
All of that having been said; We now need to look at the Prophets, which is the basis for much of Christianity as well as Judaism.
Isaiah 25:8 He will swallow up death in victory; and the Lord God will wipe away tears from off all faces; and the rebuke of his people shall he take away from off all the earth: for the Lord hath spoken [it].
Isaiah 26:19 Thy dead [men] shall live, [together with] my dead body shall they arise. Awake and sing, ye that dwell in dust: for thy dew [is as] the dew of herbs, and the earth shall cast out the dead.
Isaiah clearly believed that God would reprieve the dead, and they would rise to live again, even though it appears that his belief was that their physical bodies would be resurrected.
Daniel 12:2 and 3 And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame [and] everlasting contempt. And they that be wise shall shine as the brightness of the firmament; and they that turn many to righteousness as the stars for ever and ever.
Daniel 12:13 But go thou thy way till the end [be]: for thou shalt rest, and stand in thy lot at the end of the days.
Daniel also proclaimed a resurrection to eternal life.
Hosea 13:14 I will ransom them from the power of the grave; I will redeem them from death: O death, I will be thy plagues; O grave, I will be thy destruction: repentance shall be hid from mine eyes.
Hosea proclaimed God's victory over Death.
It is hard to understand the differing beliefs about what resurrection actually means up until the appearance of Jesus on the scene, but it is apparent that most believed in a bodily resurrection, to physical life. Even today there are variances in whether the Kingdom of God (Heaven) is a physical or a Spiritual place. However, it is obvious that until Christ there was a consensus that there would be one resurrection of the Dead, and it was generally believed that that would be a physical one.
In the scripture you quoted (Matthew 22:28 NIV) you see that precept of a physical re-emergent on the part of the Sadducees. And Jesus answer:
Matthew 22:29 through 32 KJV Jesus answered and said unto them, Ye do err, not knowing the scriptures, nor the power of God. For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven. But as touching the resurrection of the dead, have ye not read that which was spoken unto you by God, saying, I am the God of Abraham, and the God of Isaac, and the God of Jacob? God is not the God of the dead, but of the living.
Tells us several things about the resurrection.
first and foremost it says that God is the God of the living. Even though they knew that Abraham was physically dead Jesus is saying that he is still alive, making a reference to his soul. Or that part which is eternal.
They did not know the Scriptures.
Psalms 49:15 But God will redeem my soul from the power of the grave: for he shall receive me. Selah.
David is proclaiming that God will redeem his soul, and not his physical body.
- Jesus is telling them that their resurrected soul will be vastly different from their physical bodies, in that it will not be capable of reproduction as is their physical bodies.
Much is still unknown about life after death, but Jesus gave us much insight into it, and actually validated resurrection, not only by what he said, but by his own return to life.