1. The Words of the Law are Engraved on one’s Heart – Studying Mishnayot is connected to the verse, “והיו הדברים האלה אשר אנכי מצוך היום על לבבך“, let these words that I command you today be upon your heart. Torah becomes engraved on our hearts when we learn, and by memorizing the Mishnayot, we are fulfilling this pasuk.
2. Survival from the Yetzer HaRa and Bad Thoughts – The Chafetz Chaim refers to the words of our sages that say when one puts divrei Torah in his heart, the thoughts of the yetzer hara are eliminated. The yetzer hara only lives in a heart void of wisdom, so one who studies and memorizes Mishnayot will not be giving the yetzer hara a place to live.
3. Continuous Fulfillment of the Mitzvah of Talmud Torah– The Chafetz Chaim explains that knowing Mishnayot by heart allows one to do mitzvot more easily. He fulfills the mitzvah, “You shall speak of them as you sit in your house and when you walk on the way.” The Chafetz Chaim further elaborates that sometimes a person is too lazy to go to the Bet HaMidrash to learn, or he may be in a situation where he has no access to light and is unable to read. However, if he knew Torah by heart, he’d be able to learn in any situation. Even while walking, when one is unable to read, one would still be able to fulfill the mitzvah of Talmud Torah by reciting his Torah learning from memory.
4. Inheritance of the Next World – The Chafetz Chaim refers to the Zohar where it says, מי ש'יורש' מסכת” “אחת, הרי הוא 'יורש' עולם אחד, whoever inherits one Masechet also inherits one world. The meaning is not if one learns the Masechet only one time, rather if one learns the Masechet very well, by heart. It also says in the Gemara that the person should review it over and over until it is easily retrieved.
5. Receiving Honor from the Heavenly Court – The Chafetz Chaim brings down the Chazal that says, 'אשרי מי שבא לכאן ותלמודו בידו', fortunate is the one who comes here with his Torah in his hand. The interpretation of “Torah in his hand” is that he is fluent, as in the memorization of his Torah or Mishnayot.
6. The Masechet Speaks Well of You in the Next World – The Chafetz Chaim says that even if one learns Torah only one time, he fulfills the mitzvah d’orayta of Talmud Torah, earning for himself one defender. How much more so if he learns a Masechet many times until it is memorized and he is fluent. The Masechet, and the many resulting defenders will now save him from the judgments of Gehennom and bring him instead to eternal life.
7. Circumstances Specific to Old Age – The Chafetz Chaim writes that a person, both young and old, should be fluent in at least one Masechet. Especially as he ages, it is recommended he learn all kinds of Torah by heart. The reason for this is that the eyes of older people often become weak, making it difficult to study from a book. If he has committed Mishnayot to memory, he’ll be able to continue his learning and fulfill the mitzvah of Talmud Torah.
8. He Will Know What to Respond to the Heavenly Court – The Chafetz Chaim relates that when we get to the Heavenly Court we are asked, “Tell me something that you read, and a Mishnah that you repeated”. One who has committed Mishnayot to memory will be able to answer the Heavenly Court.
9. He Does Not See the Face of Gehennom – It is admirable for one to be in the habit of learning Mishnayot by heart because this is the foundation of the Torah. It is said that Asher ben Yakov Avinu is in charge of learning Mishnayot. This is hinted to in the pasuk, 'מאשר שמנה לחמו', where שמנה and משנה share the same letters. Also, for whoever is fluent in Mishnayot, Asher ben Yakov Avinu will not let him see Gehennom.
10. How to Acquire Proficiency? – The Chafetz Chaim offers some suggestions on how a person may acquire proficiency in a Masechet or in Mishnayot. If a person wants to be well versed or fluent in Mishnayot, he must act as the Sages say and learn a little bit at a time, reviewing repeatedly the little that he has learned. If he learns too much at once, he won’t be able to repeat what he has learned, and will forget everything. In addition to his regular learning, he should choose a page of Gemara or Mishnayot every week, and repeat it until it is memorized. Over time, he’ll accumulate a lot of perakim that he will have learned by heart.