The Lord Jesus was not in the heavenly sphere when He said those words. Instead, He was on the earth. Besides, Paul makes a distinction between our earthly body and our future heavenly body here:
"For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, an house not made with hands, eternal in the heavens. For in this we groan, earnestly desiring to be clothed upon with our house which is from heaven" (2 Cor.5:1-2).
Here is how Paul describes the resurrected bodies which Christians will possess when they enter the heavenly sphere:
"So also is the resurrection of the dead. It is sown in corruption; it is raised in incorruption: It is sown in dishonour; it is raised in glory: it is sown in weakness; it is raised in power: It is sown a natural body; it is raised a spiritual body. There is a natural body, and there is a spiritual body" (1 Cor.15:42-44).
So when we read that flesh and blood cannot enter the kingdom of God we know that we will not have a flesh and blood body:
"Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption" (1 Cor.15:50).
When we will enter the heavenly sphere we will possess a body which is from heaven, a spiritual body which is not a flesh and blood body. But we will remain human thereby proving that a flesh and blood body is not essential to humanity.
Earlier I said:
"But I cannot see how your ideas can possibly be reconciled to what is said at Hebrews 13:8. According to you the Lord assumed another nature at the Incarnation but yet His very nature did not change. That makes no sense to me."
To this you quoted the Confession of Chalcedon, which did not even address anything about Hebrews 13:8. Could you please address what I said in your own words. It would be greatly appreciated.
Yes, I believe that when the Lord Jesus uses the term Son of Man he is referring to His humanity. After all, why would He use the term "Son of Man" if He was saying something about His nature as God?