Κατὰ δὲ ἑορτὴν ἀπέλυεν αὐτοῖς ἕνα δέσμιον, ὅνπερ ᾐτοῦντο.

1. Κατὰ
   According to
2. δὲ
   but
   and
3. ἑορτὴν
   feast
   festival
4. ἀπέλυεν
   he was releasing
5. αὐτοῖς
   to them
   them
6. ἕνα
   one
7. δέσμιον
   prisoner
8.  
   ,
    
9. ὅνπερ
   which
10. ᾐτοῦντο
    they were asking for
    they were asking, they asked for
11.  
    .
     

But according to the feast, he was releasing to them one prisoner whom they were asking for.