καὶ νῦν εἴρηκα ὑμῖν πρὶν γενέσθαι, ἵνα ὅταν γένηται πιστεύσητε.

1. καὶ
   and
2. νῦν
   now
3. εἴρηκα
   i have said
4. ὑμῖν
   to you
5. πρὶν
   before
6. γενέσθαι
   to become
7.  
   ,
    
8. ἵνα
   so that
9. ὅταν
   whenever
   when
10. γένηται
    becomes
11. πιστεύσητε
    you may believe
    you will believe, you believe
12.  
    .
     

And now I have told you before it happens, so that when it happens you may believe.