Even in the World to Come, there is no rest for the righteous.
“They go from strength to strength” (Ps. 84:8), which is another way of conveying this notion.
When a tzaddik “graduates” from one world, finishing his learning process in this world, he is promoted to another world.
What does he gain in this whole process if he is constantly working?
What he gains through his labor are new questions, ones that he has never previously considered.
Although these are more difficult questions, they are also questions that relate to a loftier world.
He can engage in more exalted matters, but he never stops asking questions:
What is more important?
What is more fitting?
What is the proper path to take?
That is what is truly required – not to live in pursuit of tranquility, but to live in a world of questions, each one lifting a person higher and higher in his spiritual journey.
–Rabbi Adin Steinsaltz