1st John 3:1-3, “Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. And every man that hath this hope in him purifieth himself, even as he is pure.”
I think 1st John 3:3 simply means that if we abide in the Scriptures, that is, in God's promise of the Second Coming of Christ, then we are going to live as such in anticipation of His coming. The Lord Himself made this clear:Luke 12:37-40, “Blessed are those servants, whom the lord when he cometh shall find watching: verily I say unto you, that he shall gird himself, and make them to sit down to meat, and will come forth and serve them. And if he shall come in the second watch, or come in the third watch, and find them so, blessed are those servants. And this know, that if the goodman of the house had known what hour the thief would come, he would have watched, and not have suffered his house to be broken through. Be ye therefore ready also: for the Son of man cometh at an hour when ye think not.”
Jesus said if they had known when their master was returning, they wouldn't have been caught off guard not doing their jobs. The great biblical doctrine of the Rapture (Jesus' return for His saints) is one of the primary motivations to be faithful to live the Christian life.
1st John 3:3 is not saying that every believer is faithful, for we know that most are not. We see this truth taught in Luke 8:10-15 in the parable of The Sower And The Seed. Luke 8:10 says the “seed” is God's Word. There are four types of soil upon which the seed fell. There are four groups. The first group didn't get saved, because Satan took away the seed. The second, third and fourth groups all got saved, because the seeds began to grow.
The second group had shallow roots and didn't grow. They quit and lived wasted lived.
The third group was choked by the cares, riches and pleasures of this world (I think this group describes 90% of saints).
The fourth group took heed to God's Word, obeying The Great Commission to go soulwinning bearing precious seed. They bear fruit and please God. This describes less than 1% of saints today. Our text passage says that the world does not recognize Christians as God's children, because they do not know God. John 14:17, “Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.”
The parable of The Sower And The Seed is not upon getting saved; but rather, about maturing in Christ to become a soulwinner. This is abundantly clear from Luke 8:15, “But that on the good ground are they, which in an honest and good heart, having heard the word, keep it, and bring forth fruit with patience.” Soulwinning is every Christian's job.
The television, job, family, social media, video games, hobbies, politics, agendas, et cetera, hinder believers from serving God. Preaching the Gospel is every believer's duty according to Luke 8:15, Matthew 28:19-20 and John 15:5.