We just learned that Rabbi Elazar said: Be diligent in the study of Torah. Know what to answer a heretic. Know before Whom you toil. And faithful is your Employer that He will pay you the reward for your labor."
We should be continuing the chain of the teachings of the students of R. Yochanan ben Zakkai. Instead we detour to R. Tarfon. The question is why?
R. Tarfon was not at all a student of R. Yochanan ben Zakkai. In fact, the was probably not a student of Beis Hillel. Rashi to Yevamos 15b says that he was a student of Beis Shammai (remember how he laid down to say the Shema in accordance with the teaching of Beis Shammai in the first MIshna of Brochos, see this book for a discussion?). If so, why do we encounter him in this inconvenient place, right after the chapter dedicated to a different school and a different tradition?
Tosafos Yom Tov in the beginning of the third chapter of Avos says that it is because R. Tarfon says something similar to what R. Elazar just said. R. Elazar said that you Employer is faithful to pay you the wages of your labor. R. Tarfon says:
"...the day is short, the work is great, the workers are lazy, the reward is great, and the Master of the house presses."
It would seem that R. Tarfon is just amplifying what R. Elazar says, but if this is so, why does he need to say anything at all. In fact, R. Tarfon argues with R. Elazar by shifting emphasis. This becomes clear when we consider his other teaching on this topic(Avos, II:17).
He [Rabbi Tarfon] used to say, it is not upon you to complete the task, but you are not free to idle from it. If you have learned much Torah, you will be given much reward. And faithful is your Employer that He will reward you for your labor. And know that the reward of the righteous will be in the World to Come."
What does he say in this mishan that he did not just say in the previous one? Another difference is that here he says that you do not have to finish the work. Why not? Where is that dramatic sense of urgency that rang through the previous mishna? How is it not yours to finish when the day is so short, the work is so great and the Employer is pushing. Doesn't the Employer know that the work is not up to you to finish?
Well, for one thing, his previous statement is about "workers" in general, and this one is about YOU! I suggest that the main disagreement between R. Elazar and R. Tarfon in how they respectively viewed the very important question of. "What is the task of man in his world?" Is one's potential to accomplish solely in his own hands or not? What if you try and try and others do not let you succeed or they subvert your efforts?
R. Elazar, with an optimism worthy of the student of HIllel, maintained that it is all under one's control. Study Torah, don't be dissuaded from your holy task and Hashem will pay you IN THIS WORLD.
R. Tarfon understood that success is not only in the hands of the indvidual, for every person is also a part of a group. One can work very hard but if one's co-workers do not co-operate, are lazy, or just don't give a care, the one person who works very hard may also not be able to produce all that much? A more realistic picture is that "the workers are lazy" and the day is short and if they don't put out, not much gets done, no matter how hard one works.
R. Tarfon said that even then you must try. The work may not get done but it is not up to you to complete it. If you learn much Torah, whether you influence others with it or not, you will be rewarded. The work is not up to you to complete but you must work nevertheless. You will still be rewarded. Where will this reward be doled out? Not in this world, in which you accomplished but little because others did not work alongside you. The reward will be given in the World to Come, for there and only there is sincere effort appreciated in its full Glory.