Avot 2:21 He used to say: You are not required to complete the task, yet
you are not free to withdraw from it. If you have studied much
Torah you will receive much reward; and your Employer can
be relied upon to pay you the wages for your labor, but be
aware that the reward of the righteous will be given in the
world to come.
He used to say: You are not required to complete the task, yet you are not free to withdraw from it.
As an extension and amplification of verse 20, Rabbi Tarfon offers further encouragement in stressing that it is not one’s personal responsibility to complete the work God has assigned.
This reassures us of the realistic gap between aspiration and actual accomplishment. The goals we aim for might be high as we set our hearts to answer the call and to obey the will of our Father for our lives. This includes our work, relationships and leisure time, and involves spiritual growth and the control of thoughts, words and deeds in each of these areas. The daily challenge lies in living out the biblical principles of righteousness and in the practical forging ahead with the details of the task at hand. In each area we are exhorted to not be discouraged from “doing the work” due to the enormity, and at times seeming impossibility, of the task, but to understand that we must do what we can without carrying the burden of expectation to fully complete it.
In Rabbinic writings, many well-known illustrations are given of this principle. One example, from the Midrash, recounts that Emperor Hadrian saw a 100-year old man planting fig trees and asked him, perhaps sarcastically, if he hoped to ever eat any figs off of them. The old man replied, “If I am worthy I shall eat and if not, then, as my forebears have worked [to provide figs] for me, so I will work for those to come.” 
If you have studied much Torah you will receive much reward; and your Employer can be relied upon to pay you the wages for your labor…
The emphasis here is that the study of Torah, in and of itself, brings immediate blessing. In addition, our Divine Master is trustworthy and faithful to reward our work and efforts in the study of His Word as well as in all we do to implement what we learn in His service.
… but be aware that the reward of the righteous will be given in the world to come.
“Set your minds and keep them set on what is above (the higher things), not on the things that are on the earth.” (Col. 3:2 AMP)
The end of the story and the final outcome of one’s life does not occur in this world. The true and eternal reality will be revealed in the world to come when the Kingdom of God is fully established in the new heavens and earth at the end of time as we know it. We cannot measure our success or rewards in “this-worldly” terms, by natural and physical means.
A story in the Jerusalem Talmud  describes how a great scholar, Elisha ben Avuya, lost his faith in God. He saw a young man, at the request of his father, gathering eggs from a nest high in a tree. The youth first let the mother bird fly off, as commanded by Torah in what the Sages deemed the “least of the commandments” (Deut. 22:6). While climbing down, he fell and died. The reward for this specific command, together with the command to honor one’s mother and father, the only one of the Ten Commandments that promises the same, is a long life. The incident seemed to blatantly contradict the promise in the Torah and Avuya’s trust in God was shaken. His son-in-law, Rabbi Ya’akov, taught the understanding that, although some blessing may be enjoyed in this world as a result of faithful obedience, all rewards promised by God are intended for the world-to-come. He believed that if Avuya had accepted this truth his faith would have remained strong. 
Our motivation in serving Him is not for the reward but in order to live as a person of integrity, mercy and righteousness in accord with our Master’s will. In harmony with that of Yeshua and the early disciples, the vision of the Sages strongly upholds a cooperative community life, infused with peace, kindness, love and holiness. No one person can accomplish God’s redemptive plan on earth; each of us can only contribute to the whole. When we wholeheartedly support and encourage one another, in a united effort, then His Salvation breaks forth more fully in our midst.
Conclusion of Chapter 2
Rabbi Chanania ben Akashia says: The Holy One, Blessed is He, wished to confer merit upon Israel, therefore He gave them Torah and mitzvoth (commandments) in abundance, as it is said: “HaShem desired for the sake of its [Israel’s] righteousness that the Torah be made great and glorious” (Isaiah 42:21).
1. Lev. Rabbah 25:5
2. T.Y. Pesach – Hagigah 2:1
3. William Berkson, Pirke Avot, 102