English Explanation of Pirkei Avot 2:2

Rabban Gamaliel the son of Rabbi Judah Hanasi said: excellent is the study of the torah when combined with a worldly occupation, for toil in them both keeps sin out of one’s mind;
But [study of the] Torah which is not combined with a worldly occupation, in the end comes to be neglected and becomes the cause of sin.
And all who labor with the community, should labor with them for the sake Heaven, for the merit of their forefathers sustains them (the, and their (the forefather’ righteousness endures for ever; And as for you, [God in such case says] I credit you with a rich reward, as if you [yourselves] had [actually] accomplished [it all].
Rabban Gamaliel the son of Rabbi Judah Hanasi, is chronologically the last patriarch mentioned in Mishnah Avoth. Although he lived after what is normally termed the “tannaitic period” some of his statements were nevertheless included in the Mishnah. Note how this tanna’s name is slightly different. Instead of calling him “Rabban Gamaliel ben Judah” as is typical, he is called Rabban Gamaliel the son of Rabbi Judah Hanasi. This probably alludes to the high status of his father.
The first part of Rabban Gamaliel’s statement is connected to the last part of Rabbi Judah Hanasi’s statement from the previous mishnah: how does one avoid sin? Rabban Gamaliel teaches that the study of Torah is not sufficient to avoid sin, rather one should have a worldly profession as well. Together the two will keep a person busy enough that he will not have the energy to sin. This statement might also mean that because of his Torah study he will know what he is supposed to do, and because he works for his living, he will not have to steal or engage in fraudulent practices to earn money.
A person who only studies and does not work, will in the end not even be able to reap the rewards of his study. A person must somehow earn his daily bread. Furthermore, such a lifestyle will ultimately lead to sin.
The third statement probably also connects to the previous two. People who work with the community should do so for the right reasons, “for the sake of Heaven” and not for their own personal glory or profit. This also seems to be a warning against those teachers who might combine their Torah learning with their professional work. If they do so they must be careful that all of their actions are for the right reasons: to guide people in the right direction, and to bring Torah more deeply into more people’s lives, and not so they can have the benefits of being called “rabbi” or the profit of a nice salary.
Rabban Gamaliel points out that one who succeeds in working with the community should not chalk this solely up to his/her personal talents. The Jewish community has merits by the very fact of their being the children of Abraham, Isaac and Jacob, whose righteousness is bequeathed to all of the people of Israel. Nevertheless, although the success of the community is not truly based on the efforts of the community’s leaders, God says to the leaders that for their efforts they receive reward as if the community’s successes were their personal successes. In other words in a leader’s own mind he must be careful not to give himself the credit. However, God does count the tremendous sacrifices that community leaders give, and treats them as if they themselves had performed the good deeds of the community. Furthermore, even if a leader’s efforts do not result in an improvement of the community, they will receive a reward as if they had.