The object belongs to someone else, but the fool is proud of it, and shows his shallow nature.
ਨਾਨਕ ਬਿਨੁ ਬੂਝੇ ਕਿਨੈ ਨ ਪਾਇਓ ਫਿਰਿ ਫਿਰਿ ਆਵੈ ਜਾਏ ॥੧॥
naanak bin boojhay kinai na paa-i-o fir fir aavai jaa-ay. ||1||
O Nanak, without understanding, no one obtains it; they come and go in reincarnation, over and over again. ||1||
Translation by Dr. Sant Singh Khalsa
In plain words
Imagine finding a priceless jewel but having no idea what it is worth, so you carry it door to door and people offer you almost nothing. The treasure is real, but you cannot see its value on your own.
The most amazing thing is that this treasure is already inside you — the cooling Word that ends sorrow. Nanak says: without understanding, no one finds it. Without the Guru there is no understanding, so you need someone who knows its worth to help you recognize it. And once you do, you would never trade it away for pocket change.
The greatest treasure is already inside you, waiting to be recognized.
The deeper layer
Shalok, Third Mehl. A long, image-rich shalok. Central images: the jewel (maanak) the blind man cannot appraise and nearly gives away; the wealth already within the house while the world starves for it (ghar hodai dhan jag bhukhaa); the appraiser (paarkhee) who reveals its worth; and the cooling, soothing Shabad (sabad seetal) that dispels all sorrow and separation. Also: do not be proud of what is only held in trust (paraaee amaan) — humility. Without understanding, one keeps coming and going (fir fir aavai jaa-ay). The nine treasures (nau nidh) signify complete fullness.
A Question to Sit With
What good thing might you be carrying without realizing how valuable it is?
