Analysis:
This quatrain by Saadi Shirazi draws a stark contrast between the lives of the wealthy and the poor. Let's break down each line:

Line 1: منعم که به عیش می‌رود روز و شبش

"The benefactor who enjoys pleasures day and night,"
This line refers to a wealthy individual who lives a life of luxury and indulgence.

Line 2: نالیدن درویش نداند سببش

"Does not know the reason for the dervish’s lament."
The wealthy individual is oblivious to the suffering of the poor and doesn't understand the reasons behind their complaints.

Line 3: بس آب که می‌رود به جیحون و فرات

"Much water flows into the Jihon and Euphrates,"
This line refers to the abundance of resources, such as water, in certain areas. The Jihon and Euphrates are major rivers in the Middle East.

Line 4: در بادیه تشنگان به جان در طلبش

"Yet in the desert, the thirsty yearn for it."
In contrast to the abundance of water in some places, people in deserts suffer from extreme thirst.

Deeper Meaning:
This quatrain highlights the stark inequalities that exist in society. The wealthy, engrossed in their own pleasures, often ignore the suffering of the poor. The image of the flowing rivers and the thirsty desert serves as a powerful metaphor for the unequal distribution of resources. Saadi is criticizing the indifference of the wealthy towards the plight of the poor and emphasizing the need for compassion and empathy.

Key themes:

Social inequality: The quatrain highlights the vast disparities between the rich and the poor.
Indifference: The wealthy are portrayed as indifferent to the suffering of others.
Scarcity and abundance: The contrast between the abundance of water in some places and the scarcity in others is used to emphasize the unequal distribution of resources.

This quatrain is a call for social justice and compassion. It reminds us of our shared humanity and the importance of recognizing and addressing the needs of those less fortunate.