Passage
And every one that hath this hope in him sanctifieth himself, as he also is holy.
And every one that hath this hope in him sanctifieth himself, as he also is holy.
1 John 3:1 Behold what manner of charity the Father hath bestowed upon us, that we should be called and should be the sons of God. Therefore the world knoweth not us, because it knew not him.
1 John 3:2 Dearly beloved, we are now the sons of God: and it hath not yet appeared what we shall be. We know that when he shall appear we shall be like to him: because we shall see him as he is.
1 John 3:3 And every one that hath this hope in him sanctifieth himself, as he also is holy.
1 John 3:4 Whosoever committeth sin committeth also iniquity. And sin is iniquity.
1 John 3:5 And you know that he appeared to take away our sins: and in him there is no sin.
The verse centers on "hath", "hope", "sanctifieth", "himself", and "holy". It is saying that the verse draws attention to "hath" and "hope", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 2's "Dearly beloved we are now the sons..." into verse 4's "Whosoever committeth sin committeth also iniquity And...", so "hath" and "hope" belong inside that flow. In 1 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "hath" and "hope" with trust shaped by these words, not by a vague optimism outside the passage.