John 16:3-4

John 16:3-4. And these things will they do unto you, because they have not known the Father, nor me. But these things have I told you, that when the time shall come, ye may remember that I told you of them.

To be forewarned is to be forearmed, especially when the Lord Jesus Christ gives the forewarning; and his disciples were thus to be forearmed and braced up for the coming conflict.