band : 'Binding, fastening, tie, knot, band, bandage, bond, ligature, belt'. (Platts p.169)
qabaa : 'A long gown with the skirt and breast open (and sometimes slits in the armpits); a (quilted) garment; a tunic'. (Platts p.787)
firdaus : 'A garden; Paradise'. (Platts p.778)
The simile of the knot of the robe as a bud is old. By calling it a 'bud of paradise', Mirza has created freshness. It is a 'whole-world garden-- that is, the flower of this bud is better than the gardens of the whole world.
Asad, if the knot of the friend/beloved's robe would be opened, then from within, the friend/beloved's bosom and belly would emerge like a garden. So to speak, it is a bud of paradise. When a bud is opened, a flower can be seen; from the opening of this bud, a whole garden will be seen. yak-((aalam gulistaan = a whole world of a garden, many gardens.
SETS
CLOTHING/NAKEDNESS: {3,5}
For more on Ghalib's unpublished verses, see the discussion in {4,8x}. See also the overview index.
On expressions compounded with yak , see {11,1}.
This is definitely a verse of erotic suggestion; for others, see {99,4}. The speaker has a lively vision of the whole world of 'paradise/garden' glory that would be revealed if the 'bud' of the knot were to open, so that the sash would come loose and the two sides of the beloved's robe would swing apart. But how likely is it that this would happen? The second line uses two future subjunctive verbs, which places the probability at no more than fifty-fifty (and perhaps a bit less).
There's also the question of how it might happen. When a bud 'opens' (with the intransitive khulnaa ) into a flower, the process is spontaneous and unstoppable. When a knot 'is opened' (with the passive kholaa jaanaa ), the agency of human fingers is required-- and even then, the attempt doesn't always succeed; on the perversity of knots see {8,2}. The verse cleverly declines to choose either spontaneity or agency, by preferring the undecidable Persianized vaa honaa . But we know the odds of any such 'opening' are not in the lover's favor. The lover knows it too; he's really just fantasizing.
Asi:
Oh Asad, the knot of the robe of the friend/beloved is, with regard to its springtime/flourishingness, a bud of the garden of paradise. If it would open, then I would show people that a 'garden of gardens' would be seen.
== Asi, p. 232