Proof:

...there is a spiritual body... Howbeit that was not first which is spiritual, but that which is natural; and afterward that which is spiritual. (1 Cor. 15:44-46).

That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. (John 3:6).

But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you. (Romans 8:11).

And as we have borne the image of the earthy, we shall also bear the image of the heavenly. (1 Cor. 15:49).

For this corruptible must put on incorruption, and this mortal must put on immortality. (1 Cor. 15:53).

Grace to you, and peace, from God our Father and the Lord Jesus Christ. (Phil. 3:21).

21. Is a spiritual body like a mortal body?
Answer: It is like it in shape, but not in nature.

Proof:

...we shall all be changed... this mortal must put on immortality. (1 Cor. 15:51-53).

...this same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen him go into heaven. (Acts 1:11).

Behold my hands and my feet, that it is I myself. (Luke 24:39).

...we shall be like him (1 John 3:2).

Answer: A mortal body grows old, decays and dies; whereas a spiritual body lasts forever. A mortal body is weak; a spiritual body is strong. A mortal body is corruptible, lustreless, and dishonorable, whereas a spiritual body is incorruptible, bright, and glorious. Even the clothes worn by a spiritual body can become as white as snow and as shining as the sun.

Proof:

Neither can they die any more (Luke 20:36).

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: (1 Cor. 15:42-43).

They shall hunger no more, neither thirst any more; neither shall the sun light on them, nor any heat. For the Lamb which is in the midst of the throne shall feed them, and shall lead them unto living fountains of waters (Rev. 7:16-17).

have I not seen Jesus Christ our Lord? (1 Cor. 9:1) ...I saw in the way a light from heaven, above the brightness of the sun, shining round about me (Acts 26:13).

... his face did shine as the sun, and his raiment was white as the light. (Matt. 17:2).

...they shall run, and not be weary; and they shall walk, and not faint. (Isaiah 40:31).

...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 12:3).

23. Shall we ever have our mortal bodies changed into spiritual bodies?

Answer: All will experience this glorious change who believe, love, and obey the truth steadfastly to the end. They will rise from the dead at the coming of Christ, and appear before him to be judged, along with all others who are at that time brought to judgment. When he has separated them from the unfaithful, the unfaithful will be dismissed from his presence to shame, corruption, and death, while they , the accepted, will be changed in a moment: all in one company, in the likeness of the body of their glorious judge.

Proof:

...We [the accepted] shall all be changed, (1 Cor. 15:51).

For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad. (2 Cor. 5:10).

For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting. (Gal. 6:8).

...he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you... if so be that we suffer with him, that we may be also glorified together. (Romans 8:11-17).

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. (Dan. 12:2).

Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? ... And then will I profess unto them, I never knew you: depart from me, ye that work iniquity. (Matt. 7:22-23).

For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting. (Gal. 6:8).

And these shall go away into everlasting punishment: but the righteous into life eternal. (Matt. 25:46).

For they themselves shew of us what manner of entering in we had unto you, and how ye turned to God from idols to serve the living and true God; (1 Thess. 1:9).