The regular passive imperfect is recognized through يُفْعَلُ.
Active imperfect
Passive imperfect
Core change
يَنْصُرُ
يُنْصَرُ
Dammah on the imperfect prefix; fatḥah on the penultimate root letter
يَقْبَلُ
يُقْبَلُ
Dammah on the imperfect prefix; fatḥah on the penultimate root letter
يَضْرِبُ
يُضْرَبُ
Dammah on the imperfect prefix; fatḥah on the penultimate root letter
The middle vowel of the active imperfect may differ, but these regular passive forms come to the same core pattern.