FWP:
SETS == MUSHAIRAH
DOOMSDAY: {10,11}
ISLAMIC: {10,2}
VOWS: {20,2}
For background see S. R. Faruqi's choices. This verse is NOT one of his choices; I thought it was interesting and have added it myself. For more on Ghalib's unpublished verses, see the discussion in {4,8x}.
Zamin feels that the verse is about the beloved, but nothing in the verse requires that reading. Bekhud Dihlavi interprets qasam kyaa hai as implying that such an infidel's word is worthless. That's certainly possible, but we know that Ghalib doesn't compose verses that do nothing but repeat religious or moral truisms. How could we fail to look for some kind of Ghalibian twist?
And it isn't hard to find one, either. For 'what is the vow/oath of an infidel' can also imply that the infidel, not believing in Islam or any other 'faith' or 'creed', has no deity to swear by. This reading is delightfully encouraged by 'for the Lord's sake!' at the beginning of the line. This exclamation is not as strong as an oath, but it's certainly an invocation of religious authority to add force to an utterance, so it's at least a distant cousin of an oath. And ;xudaa kii qasam itself, 'I swear by the Lord!', is a well-known oath-- there's even a popular film song with that title, as a look at youtube will confirm.
This reading also takes maximum advantage of the mushairah-verse structure. The first line is verb-free and uninterpretable, but sounds potentially very severe and moralistic. Then the exclamatory 'for the Lord's sake' yields no further information. Not until the last possible moment, with qasam kyaa hai , do we get the sudden punch of the verse. And part of the punch is the piquant, slightly shocking suggestion that the chief problem of being irreligious is that then you'd have nothing to swear by!
Zamin:
In this too is that glory of realistic depiction: the beloved and then the imaginary infidelness of the imaginary beloved are accepted-- but not such that she would not believe in Doomsday and resurrection, and faith and creed.
== Zamin, p. 508