FWP:
At first glance, the second line is so reassuringly commonsensical-- the lover tells the beloved, it gives me pause to see you be cruel without reason. So it should! What more ominous alarm signal could there be, than to see a show of wanton cruelty in someone you love? Naturally it would give you pause-- and maybe cause you to turn on your heel and make a quick escape.
But needless to say, the commonsense reading has to be stood on its head. What gives the lover pause is not the sight of serious flaws in the beloved's character, or the fear of falling victim to unjust cruelty. On the contrary in fact-- what gives the lover pause is a fear of losing his precious monopoly rights over the beloved's cruelty. If she is cruel to everyone, causelessly, indiscriminately, how can her cruelty remain a special bond between lover and beloved? Her cruelty should not be lavished upon undeserving others (if it's considered a privilege), nor should it be inflicted upon helpless others (if it's considered a torment).
Like her kindness, her cruelty should be a mark of favor reserved for the true lover alone. (See {38,1} for the limit case of inappropriateness: the beloved is cruel to others, and pointedly not cruel to the lover.) The situation is serious: the very 'honor of passion' can't be maintained unless the beloved does her part, and channels her cruelty as she should. The honorable lover is as jealous of the beloved's cruelty as a lesser, worldly lover would be of her favors. (Since, of course, her cruelty is her favor, or at least as much favor as the lover is likely ever to get from her.)
In Urdu, aazaar is just a noun meaning 'trouble, affliction', etc.; in Persian, as Nazm notes, it can be used as the last member of a compound, in a participial way, like afshaan , 'scattering', and so on. Steingass gives an example (see the definitions above). The Persian-style reading is, on the face of it, more suitable: 'having seen you to be tormenting without cause'. Normally in such a usage the word must be the last member of a compound ('life-tormenting' or the like), but Ghalib is quite capable of warping Persian grammar as well as Urdu grammar; see {71,7} for a very apposite example.
Still, since we have to do something irregular anyway (by using in isolation a form that should be the last member of a compound), we might as well consider the the literal Urdu too: on that reading, the beloved herself is a causeless 'sickness, affliction, torment, trouble', etc. This makes her sound like an infectious disease, or like a balaa , something that just drops down from the heavens, for no reason whatsoever, to make our lives wretched. And in this verse, that's exactly what she is: she's an affliction that's not only dire and widespread, but also, and most pointedly, be-sabab .
This is a tarot card, the 'Queen of Swords':
Nazm:
The construction be-sabab aazaar is Persian.... Indeed, freshness in words and in poetic structure gives rise to great beauty, but it ought to be understood that when one does not have very good command of another language, not everybody has the right to make changes in usage. Here, by cruelty being universal is meant that the Rival, in whom the cause for cruelty (that is, passion) is not found-- even at him you get angry in a beloved-like way, as you do at me. (56)
== Nazm page 56