The answer is as follows:
There is no doubt that Ali did not make this statement in Medina among the Emigrants and the Helpers, who had learned as he had learned and knew as he knew. Rather, he said it only after he had gone to Iraq, by which time great numbers of people had entered Islam without knowing much about the religion. He was the leader whose duty it was to issue legal opinions to them and teach them. He therefore said this so that he might teach them and give them legal guidance.
Likewise, those Companions who lived until a later time, and whose knowledge people consequently needed, transmitted many hadiths from the Prophet—may Allah bless him and grant him peace—that were not transmitted by the four caliphs or the senior Companions. Those men had no need to transmit them, because the people around them already knew those hadiths just as they did.
For this reason, more hadiths are narrated from Ibn Umar, Ibn Abbas, Aisha, Anas, Jābir, Abū Saīd, and other such Companions than are narrated from Ali or Umar, even though Umar and Ali were more knowledgeable than all of them. People needed the former because they died later and were encountered by those who had not encountered those earlier Companions. People therefore needed to question them, and they, in turn, needed to teach them and relate hadiths to them.
Thus, when Ali said to those around him in Kufa, “Ask me,” it belonged to this category. He did not say this to Ibn Masūd, Muādh, Ubayy ibn Kab, Abū al-Dardā, Salmān, and their peers—much less would he have said it to Umar and Uthman.
That is why none of these men used to question him. Neither Muādh, Ubayy, nor Ibn Masūd ever asked him, nor did any Companion of lesser standing than they. Rather, whoever sought a legal opinion from him did so just as he would seek one from Ali’s peers among the Companions. Umar and Uthman would