Bdtyk

I found this sentence in an article. Is it some proverb? What does this mean? Below is the paragraph where I found this:

Only a waning candle sheds its light around. It is related that Abul
Hassan Ali, a jurist and friend of Al-Beruni visited him when he was
terminally ill. Al-Beruni requested him to repeat the mathematical
problem he was once discussing with him. Thinking that it was not an
appropriate occasion to talk about it, the jurist remained silent.
Al-Beruni insisted upon having a reply and said: “Is it not better to
die with knowledge then to die in ignorance?” Abul Hassan repeated
that problem to which Beruni listened intently and grasped it. A few
moments later he passed away at the age of 75 in 1048 A.D. and was
laid to rest at Ghazna. Thus, he acted upon the saying of the Holy
Prophet Muhammad (Peace and blessings be upon him): “Acquire knowledge
from the cradle to the grave.”

Note: I have googled but didn't find anything helpful.

Only when a candle is burning does it shed light. A burning candle will get smaller as it does so, which is what waning means. (The opposite of waning is waxing; the moon waxes and wanes as it goes through its monthly cycle of visibility.)

A candle which is not burning is static. It doesn't get smaller, but nor does it shed light. It is not making any progress towards its end, its 'death'.

The simile is to human life. If you do not constantly acquire knowledge through life, you are not burning, you are merely static and stagnant with nothing useful to offer. A person who constantly acquires knowledge is like a candle burning, always offering light to those around it on its way to its natural end.

A version of this proverb I've seen more often is: "The candle burns brightest just before it goes out." For example:

But, as the old cliche says, perhaps a candle burns brightest just before it goes out.

(Lawrence J. McCaffrey, Textures of Irish America, 1998)

Quite often, a candle will get a burst of radiant light just before it flickers out, and some people have used that phenomenon in a metaphor.

In this case, someone is sharing valuable information just before they pass away.

Sit at your desk or table with a new (tall) candle and you'll notice the wax in the candle stem actually causes a shadow beneath the flame. Once the candle burns low, the shadow disappears as the flame gets closer to the desktop surface. Without the tall stem of wax, the light illuminates the desktop or table surface more completely.