What is our blessed hope?
The blessed hope is the sure expectation that when Christ returns, believers who have endured in righteousness will be changed from these corruptible, mortal bodies into glorious, incorruptible, celestial bodies like Christ's own, and will live forever with Him.
Scripture teaches that God has subjected the sons of men to hope, a great expectation that there is something better than this present world offers. Romans 8:18 to 23 shows that creation groans and travails, waiting for the manifestation of the sons of God, and that believers who have the firstfruits of the Spirit groan within themselves, waiting for the adoption, the redemption of the body. This is the hope we were subjected to: deliverance from the bondage of corruption into the glorious liberty of the children of God.
The blessed hope is the expectation of being changed into a glorious, celestial and immortal state at Christ's return. As it is written, this corruptible must put on incorruption, and this mortal must put on immortality, and in a moment, in the twinkling of an eye, at the last trump, the dead shall be raised incorruptible and the living shall be changed. Paul also describes it as having a building of God, a house not made with hands, eternal in the heavens, so that when this earthly tabernacle is dissolved we are clothed upon with a heavenly one, and mortality is swallowed up of life.
This hope includes eternal life and a new, incorruptible, celestial body like Christ's own, free from pain, sickness, and death. When He appears, we shall be like Him, for we shall see Him as He is, and everyone who has this hope purifies himself, even as He is pure. Those who receive these transformed bodies will also rule and reign, having dominion over creation, including the Gentiles who remain after Christ's return, for the first thousand years, in bodies no longer confined by the flesh.
This is called the blessed hope because although it has not yet been seen, it is held with patience and full assurance. We are saved by hope, and hope that is seen is not hope; but if we hope for what we do not see, then we wait for it with patience. God has given us the earnest of His Spirit as a witness within us that this promise is faithful, and those who endure in righteousness to the end, making their calling and election sure, will receive an abundant entrance into the everlasting kingdom of the Lord.
The scriptures
For I reckon that the sufferings of this present time are not worthy to be compared with the glory which shall be revealed in us. For the earnest expectation of the creature waiteth for the manifestation of the sons of God. For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope, Because the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God. For we know that the whole creation groaneth and travaileth in pain together until now. And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.
For we are saved by hope: but hope that is seen is not hope: for what a man seeth, why doth he yet hope for? But if we hope for that we see not, then do we with patience wait for it. Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. And he that searcheth the hearts knoweth what is the mind of the Spirit, because he maketh intercession for the saints according to the will of God.
Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed, In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed. For this corruptible must put on incorruption, and this mortal must put on immortality. So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. And every man that hath this hope in him purifieth himself, even as he is pure.
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: If so be that being clothed we shall not be found naked. For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life. Now he that hath wrought us for the selfsame thing is God, who also hath given unto us the earnest of the Spirit. Therefore we are always confident, knowing that, whilst we are at home in the body, we are absent from the Lord: (For we walk by faith, not by sight:)
Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall: For so an entrance shall be ministered unto you abundantly into the everlasting kingdom of our Lord and Saviour Jesus Christ.
Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself.
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.