M6:66 — آب جیحون را اگر نتوان کشید / هم ز قدر تشنگی نتوان برید

Translation: Even if one cannot draw all the water from the Jeyhun (Oxus) river, One cannot cut off (be deprived of) the measure of one's thirst.

Meaning: This couplet suggests that while infinite divine truths and vast spiritual knowledge may be beyond full human comprehension or articulation, one's spiritual thirst and longing will always be met, at least in proportion to its intensity.

This couplet is one of the most crucial passages for understanding Rumi's approach to the world of knowledge and the mission of the Mathnawi. Rumi offers it following a grand description of the dominance and sway of the Prophets, especially the Prophet of Islam, in both the corporeal and spiritual worlds. After stating, "the explanation of this dominance will not fit in the mouth," he adds this couplet. This 'dominance' and sway of the Prophet is itself like the 'Water of Jeyhun'—truths so vast and boundless that they cannot easily be contained within the framework of language and expression, and intellects are incapable of encompassing them.

However, Rumi intricately weaves two subtle points here. First, the issue of the 'inexpressibility' and 'indeterminacy' of certain sublime truths. This is a reality acknowledged by mystics and philosophers alike: that there are realms of existence that transcend the limits of our words, concepts, and even conventional perceptions. The Water of Jeyhun, in other words, is a metaphor for the boundless sea of meanings that Rumi himself alludes to in the prologue to the first book of the Mathnawi: "It is the sea of divine knowledges that are not unveiled to any human save the chosen saints." This vast river symbolizes infinite grace and endless divine knowledge that cannot be fully drawn or contained, just as one cannot confine all the light of the sun in a vessel.

The second point, however, is hopeful and comforting: "One cannot cut off (be deprived of) the measure of one's thirst." This 'thirst' can be understood as humanity's yearning, passion, quest, and inner capacity for receiving spiritual truths. Rumi asserts that although you cannot draw all the water of the Jeyhun, you will not be denied your portion according to your thirst. This means that even if the entire truth is not unveiled to you, you will receive a benefit commensurate with your longing and existential capacity. The Mathnawi, in Rumi's own words, "is an island in the sea of meaning"—a place where the thirsty can tread and drink from that divine grace according to their own measure. This is a promise: no thirsty soul will remain unquenched, and no seeker will return from the path empty-handed. God Almighty is too generous to leave the thirsty unanswered, even if His ocean is boundless and ineffable.

This couplet inherently demonstrates both the limits of human understanding and expression, and simultaneously promises the unending bounty and grace of the Divine. That 'thirst' is not merely a deprivation but also the criterion and measure of reception. The thirstier one is, the more one drinks. This is a fundamental principle in Rumi's mysticism: the extent of reception is contingent upon the seeker's capacity and longing, not solely upon the vastness of divine grace, which is always infinite.

Key takeaways

• Divine truths transcend the full scope of human comprehension and expression.
• Human spiritual thirst and longing are never left unquenched.
• The measure of receiving divine grace is proportional to the seeker's capacity and depth of yearning.
• Rumi's Mathnawi itself serves as an 'island' where the thirsty can find their fill of spiritual insight.