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.
Therefore the world — The Jews, and all who know not God, and are seeking their portion in this life; knoweth us not - do not acknowledge, respect, love, or approve of us. In this sense the word γενωσκειν is here to be understood. The world KNEW well enough that there were such persons; but they did not approve of them. We have often seen that this is a frequent use of the term know, both in Hebrew and Greek, in the Old Testament and also in the New.