Mishnah 16 - Chapter 2 - Pirkei Avot

Hu hayah omer. Lo aleicha hammelachah ligmor, velo attah ven chorin libbatel mimmennah. Im lamadta torah harbeh, notenim lach sachar harbeh. Vene'eman hu ba'al melachtecha sheyeshallem lach sechar pe'ullatach. Veda', mattan secharan shel tzaddikim le'atid lavo.

He [Rabbi Tarfon] used to say: It is not your duty to finish the work, but neither are you at liberty to neglect it; If you have studied much Torah, you shall be given much reward. Faithful is your employer to pay you the reward of your labor; And know that the grant of reward unto the righteous is in the age to come.

He (R. Tarfon) was wont to say: The work is not yours to complete. [The Holy One Blessed be He did not hire you to complete all of it, in which instance you would lose your wage if you did not complete it.] And [lest you say: (In that case,) I will not learn and I will not take a wage] — you are not free to abstain from it. [Perforce the yoke is upon you to labor.] If you learn much Torah, you are given much reward, and Your Employer is trusted to pay you for your labor. And know that the reward for the righteous is in the world to come.