By the touch of philosopher’s stone - Paaras sang paras kay

              Paaras kai sang paras kay Kanchan bhayi talvaar

               Tulasi teenon na mitay- Dhaar, Maar, Aakar 

“By the touch of the philosopher’s stone, the sword turns into gold.
But, says Tulsidas, its sharpness, its edge, and its form remain unchanged.”

Through this couplet, Sant Tulsidas—the revered composer of the Ramcharitmanas—brings forth a profound truth about spiritual life.

(This example is drawn from an old belief found in many ancient legends - not only in Indian traditions but also in Western legends, Greek mythology, and Arabic literature—that any metal that came in contact with Paras or the philosopher’s stone would turn into gold. 

Greek mythology and Arabic literature also talk about the miraculous waters like Aab-e-Zamzam.)

By using this analogy as an illustration, Sant Tulsidas says:
An iron sword, when touched by the philosopher’s stone, transforms into gold, but its form and qualities do not change.
Despite this transformation, its original form and qualities - its sharpness and functionality remain the same.

Of course, it becomes brighter, its value multiplies, and it becomes attractive and admirable.
But its form does not change—nor does its razor-sharp edge, nor its destructive quality.
Even though it is now gold, it still has the capacity to wound. 

It retains the potential to injure anyone who crosses its path.
If anyone tries to press it down, obstruct it, or stand in its way, it can still cut through.
It is still a sword, with the same sharp edge, the same cutting power, and the same destructive ability.

Similarly, when a person gains knowledge, attains Gyana, comes in contact with satsang and the holy company of saints, their life may become brighter. 

They may gain honor, respect, fame, and success.
But a person’s innate nature rarely changes.
Those who are naturally humble remain humble.
And those who are filled with pride and arrogance continue to display the same tendencies, even in spiritual circles.
Those who have an inherent desire to lead and display themselves continue to seek recognition even in spiritual realms. They always strive to stay ahead of others and control everything around them.

This raises a question:
Does human nature never change?

In the next couplet, Saint Tulsidas gives a solution:

                 Gyan Hathauda jehi milay - Satguru milay Sunaar

                    Tulasi teenon mit gaye - Dhaar, Maar, Aakar 

“With the hammer of wisdom and the guidance of a true Guru,
The sharpness, the edge, and the form of the sword can all be reshaped.”

A sword’s edge and form can be changed by repeated hammering.
It can be reshaped into a golden pot, golden jewelry, or a golden sculpture.
The constant striking of the hammer not only transforms its form and appearance but also its destructive qualities.

Similarly, listening to the words of saints repeatedly, reflecting upon them deeply, and allowing wisdom to penetrate the heart, works like the hammer that slowly reshapes human nature. 

But the change will come only if the blows of knowledge strike the heart, not just the ears.

The transformation can happen only if the words of wisdom do not merely fall upon the ears but strike deeply into the heart - 
Otherwise, no real transformation takes place.
                              " Rajan Sachdeva "

Note:

Interestingly, it's called the Philosopher's stone - meaning it's a philosophical metaphor rather than a physical reality.