Passage
For this is the declaration which you have heard from the beginning, that you should love one another.
For this is the declaration which you have heard from the beginning, that you should love one another.
1 John 3:9 Whosoever is born of God committeth not sin: for his seed abideth in him. And he cannot sin, because he is born of God.
1 John 3:10 In this the children of God are manifest, and the children of the devil. Whosoever is not just is not of God, or he that loveth not his brother.
1 John 3:11 For this is the declaration which you have heard from the beginning, that you should love one another.
1 John 3:12 Not as Cain, who was of the wicked one and killed his brother. And wherefore did he kill him? Because his own works were wicked: and his brother's just.
1 John 3:13 Wonder not, brethren, if the world hate you.
The verse centers on "declaration", "heard", "beginning", "should", "love", and "another". It is saying that the verse draws attention to "declaration" and "heard", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 10's "In this the children of God are..." into verse 12's "Not as Cain who was of the...", so "declaration" and "heard" 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 "declaration" and "heard" with trust shaped by these words, not by a vague optimism outside the passage.