The apostle Paul claimed to have gotten his message directly from the Lord Jesus, thus claiming that his writings were inspired by God. In 1 Corinthians 15, Paul tells us the following:
Now if Christ is proclaimed as raised from the dead, how can some of you say that there is no resurrection of the dead? 13 But if there is no resurrection of the dead, then not even Christ has been raised. 14 And if Christ has not been raised, then our preaching is in vain and your faith is in vain. 15 We are even found to be misrepresenting God, because we testified about God that he raised Christ, whom he did not raise if it is true that the dead are not raised. 16 For if the dead are not raised, not even Christ has been raised. 17 And if Christ has not been raised, your faith is futile and you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If in Christ we have hope in this life only, we are of all people most to be pitied. (1 Cor. 15:12-19)
Here the Bible clearly tells us that if no people are raised from the dead, then Christ is not raised and we are all still in our sins, destined for an eternity separated from God. It further clearly connects the physical, bodily resurrection of all Christians with whether those who have fallen asleep (died) having perished. Therefore this passage teaches that we will all rise from the dead in our physical bodies, and this is key to our spending eternity with God.
The last verse quoted above, v.19, seems to have no concept of spirit-only humans. The reason is that the Bible was not influenced by Plato’s philosophy, by which Augustine and many others have been influenced. Most of us, whether we know it or not, have been influenced by Plato. Platonic philosophy teaches that the “real you” is your spirit, and at death our present physical bodies are left behind, never to be taken up again. However, 1 Corinthians 15 and Phillippians tells us the contrary, that our bodies will be raised and changed, transformed to be like Jesus’ resurrected body.
The Bible’s concept of humans is that we are a soul-body unity, and our body is as much a part of us as our soul. Without a physical, bodily resurrection, the entity that is “you” has been conquered by death. We know we will be raised due to Jesus having been raised.
For more information on the idea of a soul-body unity, see here. For an apologetic case that presents a logical, reasonable explanation of the resurrection of Jesus, see Gary Habermas, The Case For The Resurrection of Jesus. Habermas also published a lengthy discussion he had about resurrection with prominent academic atheist Anthony Flew, a book titled Did The Resurrection Happen?