FWP:
SETS == A,B
An ordinary journey includes occasional trees, rocks, walls, buildings, etc. that provide shadows in which the traveler can rest; it also includes tents, camps, and caravansarais where he can pass the night. The journey of passion takes place in no ordinary desert: the only sleeping-place available is a shadow, and the only shadow available is one's own. This verse reminds me of the astonishing {16,4}, with its fiercely glittering mirages.
It's impossible to be sure of what it means that the speaker 'at every step considered his own shadow to be a bedchamber'. Perhaps it's a sign of weakness (he is so utterly prostrated by fatigue that as he staggers along he sees phantom 'bedchambers' everywhere). But it might well be only the (personified) 'Weakness', in the first line, that is so exhausted and desperate. The condition of the speaker himself might be quite different.
For in this 'A,B' verse, there might well be a contrast between the two lines. While 'Weakness' seeks rest and comfort in the first line, in the second line the speaker could be celebrating the contrast with his own strength and determination; he might even be boasting a bit. Perhaps he is so indefatigable that his own shadow is all the 'bedchamber' he needs, and with every footstep (which lies down flat on the ground) he is as refreshed as if by a night's sleep. This reading resonates with the defiantly ebullient mood of {11,1}, which also offers unusual imagery about footsteps.
The verb samajhnaa can mean not only 'to understand' (accurately), but also 'to consider' (subjectively, perhaps inaccurately); on this see {90,3}.
Nazm:
Where the night is spent, there is the bedchamber. That is, at every step, I saw my shadow and considered that night had come and the halting-place had been reached. (34)
== Nazm page 34