John Gill emphasizes that believers should not be surprised by the hatred they face from the world, as this animosity has existed since the fall of man. He explains that the world, representing the wicked, harbors hatred towards the saints simply because they are chosen and live righteously, contrasting with the sinful nature of the world. This enmity is a historical constant, illustrated by biblical examples such as Cain and Abel, and the persecution of prophets and apostles. Gill reassures believers that such opposition is a common experience for those who strive to live godly lives in Christ Jesus.

Ver. 13. Marvel not, my brethren, if the world hate you. By "the world" is meant the inhabitants of the world, the wicked part of them; these hate the saints, though without a cause, any just cause, and for no other reason, but because they are chosen and called out of the world, and do not live the wicked life they do: and this hatred of theirs is not at all to be wondered at; so it was from the beginning, and has been in all ages since; immediately upon the fall there was enmity between the seed of the woman and the seed of the serpent, which showed itself in Cain, the instance just given, who hated and murdered his righteous brother; Ishmael, that was born after the flesh, persecuted Isaac, that was born after the Spirit; and as it was then, it is now, the Jews persecuted the prophets of old, and hated Christ and his apostles. This is the common lot of all the saints, of all that will live godly in Christ Jesus; and therefore it should not be reckoned a strange and unusual thing; it always was so, even from the beginning, as soon as ever there were two sorts of persons, good and bad, righteous and wicked. This is a corollary or conclusion drawn from the above instance of Cain.