Charles Ellicott Commentary John 15:18

"If the world hateth you, ye know that it hath hated me before [it hated] you." — John 15:18 (ASV)

If the world hate you.—He has spoken of their close union with Himself, and of their love to each other. He proceeds in the remainder of the chapter to speak of their relation to the world. There is a striking contrast between the “love” in the last verse, and the “hatred” in this. There was the more need for them to be closely bound to each other, and to their Lord, on account of the hatred which awaited them in the world.

You know that it hated me before it hated you.—It is better to take the first word as an imperative, “Know that it hated . . .” The very hatred, then, is a bond of union with their Master, and this thought should supply strength to meet it, and joy even when suffering from it (John 15:11). (Compare to 1 Peter 4:12–13.)