Book of 1 John Chapter 3 Vs. 13

 Love One Another

1 John 3:13 "Marvel not, my brethren, if the world hate you."

Marvel not, my... Expect no better treatment from the world than Abel received from Cain.

brethren (ἀδελφοί)

The only occurrence of this mode of address in the Epistle.

if the world... History is filled with stories of the persecution of the saints by the world (Heb. 11:36-40). This does not surprise believers because hateful Satan is their father, verse 10.

hate (μισεῖ)

Indicative mood, pointing to the fact as existing: if the world hates you, as it does.

Jesus warned His followers that they would be despised (John 15:18-25).

It is not a thing to be concerned about, if the world hates you, Christian. They hated Jesus our Leader, and they will hate us, also. The real reason they hate us, is because we remind them of the life they are living.

Their guilt comes before them more, when they are around those who are trying to live right. We are not of the world. We are a separated people. Christians are even spoken of as peculiar. This means peculiar to the world.

Such reactions of hatred and murder (1Jhn. 3:11-12) are also worldly, since the world hates Christians. That fact should not surprise the readers called brothers only here in 1 John at all, however. What else can the world be expected to do? It is hatred among believers that is so abnormal, and against which John was fundamentally warning. In that sense it is right to treat this verse as more or less parenthetical.