(15) Whosoever hateth his brother is a murderer. (16) we ought to lay down our lives for the brethren. 1 John 3:15-16.

Apostle John uses strong language to call out anyone who hates a brother or sister. John calls such haters murderers!

To be perfected in love, there may not be any trace of hatred in us towards anyone.

1 John 2:9-11 ASV
(9) He that saith he is in the light and hateth his brother, is in the darkness even until now.
(10) He that loveth his brother abideth in the light, and there is no occasion of stumbling in him.
(11) But he that hateth his brother is in the darkness, and walketh in the darkness, and knoweth not whither he goeth, because the darkness hath blinded his eyes.

1 John 3:13-17 ASV
(13) Marvel not, brethren, if the world hateth you.
(14) We know that we have passed out of death into life, because we love the brethren. He that loveth not abideth in death.
(15) Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.
(16) Hereby know we love, because he laid down his life for us: and we ought to lay down our lives for the brethren.
(17) But whoso hath the world's goods, and beholdeth his brother in need, and shutteth up his compassion from him, how doth the love of God abide in him?