Pirkei Avot - Ethics of the Fathers

~Level 1~
Bartenura - "he who studies [torah] in order to teach" - i.e. one who learns in order to be learning torah always, but he does not intend to bestow kindness to the public. For example "Rava" who "toiled in torah but did not toil in gemilut chasadim (acts of kindness)" (Rosh Hashana 18a).

Even though one should also toil in acts of kindness, but nevertheless G-d helps him to learn and teach and his intent is fulfilled.

"he who studies torah in order to practice" - he wants to toil in torah and also to bestow kindness to others, like Abaye who toiled in both. G-d helps him to fulfill his intent and he will merit to learn, teach, guard, and fulfill.

~Level 1~
Tiferet Yisrael - "he who studies [torah] in order to teach" - this is not referring to one who wants to learn only and not practise. For then he would be a Rasha (wicked person).. and our sages said "one who learns torah not for its sake, the torah becomes a deadly poison to him" (Taanit 7a).. Rather it refers to mitzvot which don't have action like emunot v'deiot (philosophy of faith) or laws not relevant to everyone like divorce laws.. or studying the laws of Kodashim (temple offerings) for a non-kohen or the laws of tumah and taharah (ritual impurity) in our times.

~Level 2~
Rabeinu Yonah - "he who studies [torah] in order to teach" - this is not referring to one who learns in order to teach but not to do. For then he is not granted the ability neither to study nor to teach. Rather, it refers to one who does not toil and examine too deeply lest he find a prohibition in the permitted things. He learns the simple meaning only in a superficial manner. Thus he is given only the ability like his thought - to learn and teach only.

"he who studies torah in order to practice" - i.e. his intent is to delve deeply in order to know the truth of the matter. He is willing to toil days and even years to know a small matter and conduct himself according to the truth. This person is considered "learning in order to practise". For all his primary intent is that the action [he does] should be true. Therefore, "he is granted the ability to study, to teach, to guard, and to practice". For all this is included in the [true] act.

~Level 3~
Rabeinu Avraham Pritzel - "he who studies in order to teach..." - among those who learn torah, there are different levels. Some learn torah in order to teach others or because it is delightful, i.e., he loves to learn torah because it is good. Some learn in order to live [eternally] through it or to elevate oneself and rule over others. Some learn in order to fulfill the torah of G-d, for action is the primary thing.

Therefore, this sage came and mentioned two important levels. For one who learns torah in order to merit others to its qualities - this is a good thing and G-d will grant him the merit to learn and teach others.

In this level he did not mention the aspect of practise. For this preliminary level will suffice [to elevate him] since certainly "from doing it not for its sake, he will come to do it for its own sake" (Pesachim 50b, mitoch shelo lishma ba lishma).

The second level, "one who learns in order to practise", merits all these blessings. This comes to teach that the primary matter is action and this is the true purpose.

For one who learns torah to know its statutes and commandments in the way of "you shall study them and guard to do them" (Devarim 5:1) - he will merit to learn and teach, guard them in his heart and not forget them and fulfill them forever..

~Level 4~
Matanat Avot - Sometimes we find two people who are equally intelligent and understanding. They may even be equally diligent. But nevertheless one grows much more than the other. For one wants to know only one or two tractates. This is all he wants. Therefore in the Siyata d'Shmaya (divine help), this is all he gets and no more. But his fellow knows that besides this tractate that they are learning in his yeshiva or kollel, there is also an entire Shas (talmud) and its commentaries, Rambam, Tur, Shulchan Aruch and its commentaries and endless responsa (shayla teshuvot). He aspires and hopes and prays to know everything.

Therefore, he merits divine assistance to know everything. For according to his request is his assistance.

Let us now explain the difference between them.

"one who learns in order to teach" - this refers to a man who sits and toils in torah with great diligence. When he encounters a difficult sugya (talmudic discussion), he musters great strength and plows it forwards and backwards in all its details and fine points. Why does he do this? Because he wants to attain clear understanding in the sugya until he can teach it clearly to others.
(as they say: "he who wants to check if he learned something properly, let him check if he is able to explain it to a young child. If he succeeds, it is a sign that he understood properly".)

What does such a person merit? He merits to truly understand the sugya clearly and perhaps he will even merit to actually teach it and explain it to others.

"he who learns in order to do" - here it is referring to one who learns exactly like the previous person. But in all the details and fine points that he finds in the sugya, he also aspires to conduct himself according to them, meticulously following the Halacha (Jewish law) exactly as he learned.

He merits divine assistance to guard all the fine points and stringencies. Likewise, since people observe that he is meticulous in all the details of Halacha, they realize that he has great knowledge in torah and thus they flock to him in order to learn from the radiance of his torah. Thus, he merited to guard and do and also to learn and teach..

Thus, one who is truly careful to guard meticulously all his ways and conducts, whether in matters between man and G-d or between man and his fellow, then, besides that he will merit divine assistance in continuing to guard the details and stringencies, but he will also merit to teach others the proper path by his very conduct.

Thus we find that for every great Rabbi that passes away, books are printed on his conduct and ways. This is besides his books on Halacha and responsa etc.

For one who is meticulous in all his conducts to the utmost extent, he is fit to serve as an example and role model to everyone.