Behold, how great a love the Father has bestowed on us, that we should be called children of God! For this cause the world doesn't know us, because it didn't know him.

 John goes on to ask why Cain murdered his brother; and his answer is that it was because his works were evil and his brother's were good. Then he drops the remark: "Do not be surprised, brothers, if the world hates you." 