لَوْ تَزَيَّلُوا لَعَذَّبْنَا الَّذِينَ كَفَرُوا مِنْهُمْ عَذَابًا أَلِيمًا
“If these (believers) had been separated from them, We would have inflicted a grievous punishment on the disbelievers”
Ibrahim Al-Karkhi said, I said to Imam Sadiq (as), May Allah amend your affairs! Was Imam Ali (as) not strong in (supporting the) religion of Allah?
Yes (he was), Imam (as) replied.
Then how did people overpower him and what prevented him from defending (himself) against the people? I asked.
You asked, so understand the answer. A verse in the Book of Allah prevented him, the Imam (as) said.
Which verse? I asked.
Imam (as) replied, “If these (believers) had been separated from them, We would have inflicted a grievous punishment on the disbelievers”
Allah had entrusted (many) believers in the backs of disbelievers and hypocrites. Therefore, Ameerul Momeneen (as) did not kill the fathers until the entrusted (believers) were born from those disbelievers. However, when the believers were born from their fathers, he (as) fought their fathers and killed them.
The same applies to our Qaem (as). He will not reappear until the entrusted (believers) of Allah appear (from the backs of the disbelievers), after which the Qaem (as) will rise against the disbelievers and kill them. (Kamaluddin volume 2 page 461; Tafseer Al Qummi volume 2 page 316)