Compare the same grammatical position in active and passive voice.
PassiveActivePosition
لِيُفْعَلَنَّلِيَفْعِلَنَّsingular masculine Ghaa'ib
لِتُفْعَلَنَّلِتَفْعِلَنَّsingular feminine Ghaa'ib
لِأُفْعَلَنَّلِأَفْعِلَنَّMutakallim singular
The Heavy-Noon ending stays part of both forms; the voice changes through the verb's vowel pattern.