Of course, knowledge of Arabic alone is not enough. That is why, in
this thread about being a Taalib-ul-`Ilm, I explained some of the required Islaamic sciences one is required to have mastered before they can even attempt to be deriving rulings from Qur'aan and Sunnah.Also, that Imaam Ahmad memorised one million Ahaadeeth is no exaggeration. The A'immah of the past, especially the Arabs, had extremely powerful memories. Even in these days, when the memories of people have become so weak on account of the luxury of having computers and smartphones, there are still people with powerful memories. Even myself, Alhamdulillaah, I am able to read a Hadeeth just once and memorise it. During the period when I did Hifz, I used to do 10 pages of Sabaq a day. That's memorising 10 pages a day, and I was able to do it within an hour or so, Alhamdulillaah. I did the entire 26th Juz/Para as Sabaq in one day. When it came to Soorah an-Noor, I memorised the entire Soorah within one night. The Arabs of today still have very good memories, Alhamdulillaah.So, for Imaam Ahmad ibn Hanbal, who lived over 1,000 years ago, to memorise one million Ahaadeeth is not at all difficult to believe. He was not the only Imaam who did this. Imaam Abu Zur`ah ar-Raazi memorised 700,000. Imaam al-Bukhaari memorised 300,000. When Imaam Ahmad was asked how many Ahaadeeth one must have memorised in order to be a Mujtahid, he hinted at 400,000 "perhaps" being enough. These are historical facts narrated in the books of history. You cannot just reject historical facts because they seem impossible to you. If you can reject these historical facts, what's to stop another person from coming along and saying that he denies that the Ambiyaa ever existed? He denies that Nabi Moosaa عليه السلام existed, or Nabi `Eesaa عليه السلام, or any of the other Ambiyaa? Or, another person can come along and say that he denies Adolf Hitler ever existed, or Stalin, or Marx, or Benjamin Franklin, or Abraham Lincoln; he denies that World War I and World War II ever took place, he doesn't believe that the Native Americans, Wild Indians, ever existed, etc. Using that logic, anyone could just reject anything and everything because he "feels like it". Maybe it "seems impossible" to him that World War I took place, so he rejects it. He can also say it's "not Kufr or Shirk" to reject it. Yes it's not Kufr or Shirk: it's simply Jahaalat (ignorance). There were historians who specialised in history. They made it their life's goal to just record historical events. Especially when it comes to Islaamic history, the Muslim historians spent a great deal of effort providing evidence for each of the facts they wrote down, and so they would have Asaaneed (chains of narrators) for each of the historical events, and there was the science of narrator criticism to determine the honesty and trustworthiness of each narrator in the chain, etc.So, long story short: Imaam Ahmad ibn Hanbal memorised one million Ahaadeeth. What's hard to believe about that? We, as people who did Hifz, memorised the Qur'aan, 848 pages long. 848 pages! And there are thousands of Huffaaz around the world - especially in the Indo-Pak subcontinent - able to recite the entire Qur'aan from memory in one day. Many of them do that during Ramadhaan, Taraaweeh. Reciting the entire Qur'aan from memory in a single night.Was-Salaam.